Frosty

I assume your overflow is a hose that dumps on the ground. I have installed an inexpensive coolant recovery catch can on my '72 Lemans with a 455/4-core radiator. A 3" x 10" is what I have. I bolted it to the radiator support. I used one existing hole and drilled a second. I mounted it literally right next to the radiator and connected the overflow hose to the input line of the recovery can. No more leaking antifreeze. When the radiator cools down, vacuum will draw the coolant back into the radiator.
 
https://www.speedwaymotors.com/Search?query=coolant recovery tank
 
This is just one example. Many catalog stores have these sort of items. Summit, Jegs, etc.
 

Your car, your wallet, your rules. These are some of my suggestions.
A front disc brake conversion would be an excellent safety upgrade.
A mild custom cam to tweak performance of your inline 8 without going crazy.
Consider installing an overdrive automatic transmission or adding a Gear Vendors Overdrive kit if you want to keep the manual tranny - to get better highway economy.
New shocks, replace all the suspension bushings and body mounts with new ones. Most, if not all, are shot, sagging or rotting.
Install a rear sway bar if you car doesn't have one.
Definitely replace every bit of rubber vacuum hose and rubber fuel lines on the car. This is mostly a safety issue. If your hoses are still original, then they were made at time when unleaded and ethanol fuels didn't exist. Ethanol will destroy old hose from the inside out and raise the potential for a failure or possible fire. Today's modern hoses are made to deal with the effects of ethanol.
Carb rebuilt kit with parts to handle ehtanol fuel
Harden seats on the valves to handle unleaded fuel
 
THose are my suggestions without trying to break the bank and keep the car mostly stock.
 

The wire should slide off the sensor. There maybe a clip that you have to compress to get it to release. This will deactivate your temperature gauge on the dash in the process. Once you have the wire off, you can take a socket to remote it. Just remember that this sensor is submerged in coolant, so you should expect coolant to leak out. So be prepared to plug it up with something else ASAP. Otherwise you will have a mess.

Assuming the car has not been abused in any serious way (hey it's Trans Am after all), then basic preventative and proactive maintenance such as oil changes, radiator flush -n fills, tune ups, etc. will do you well.
I would encourage you to replace every rubber vacuum and rubber fuel line in the car as a safety precaution. If the hose is original, it was installed when ethanol fuels were not available. Today's modern ethanol fuels breaks down old hoses from the inside out. Time, grime, and UV light wears then down from the outside. Today's modern hose is design to handle ethanol fuels and prevent break downs or worse, a vehicle fire.

For gaskets and seal kits for the 239, I recommend:
 
Egge Machine  https://egge.com/product/intake-exhaust-manifold-set-17/
Kantor Auto Parts  https://www.kanter.com/
 
Kanter may also have the motor mounts you are looking for

I would check under your car. I suspect that when Pontiac shipped your vehicle to Superior Coach in Mississippi that it was an original 124" wheel base chassis. GM use to send commercial chassis (CC) cars out with the front clip and windshield installed and the doors, bumpers, and rear quarters were neatly packed onto the chassis since the coach builder would be adding the roof/upper body and detail out the rest of the car..
I think your hearse has had the chassis lengthened by Superior for hearse/ambulance duty. I would look underneath the chassis (front to back) for possible cut/welded extension pieces.
So depending on what you need, I suspect that you need to find a donor 124" chassis, preferable either a convertible or a wagon chassis. Convertibles have added frame stiffeners to support the car with the loss of the roof. A wagon chassis for obvious reason - it is the closest to your car.

IS this what you are looking for?
https://www.museumofamericanspeed.com/1956pontiacsedan.html
 

I would call either OPGI or Ames. I think there was a specific wind lace trim that was the filler between the armrest and door frame. I'd be surprised if that was not reproduced.

So are you saying I need to get another knee brace to just push in the clutch?
Greeeeeaaaaatttt!

I think this paint chart might be of some use too.
http://www.pontiacpower.org/enginecolor.htm
 

I see no reason why you cannot use a modern shock on a car that old. You simply need to measure the length you need for your ride.
How to Measure Shocks
A shock is measured by its extended and collapsed lengths, and is measured from the center of the loop mount or the base of the stud mount. To get the extended length of a shock, remove it from the vehicle and allow it to expand on its own or pull it to the fully extended position and take a measurement. To get the collapsed length of a shock, compress it by hand or by using a strap and take a measurement. With the expanded and collapsed lengths of your current shocks, you will be able to find a suitable shock for your custom application.

I agree with everything JUSTA said. I have ordered from all of them. There is also YearOne out of Georgia.
I tend to order more from NPD simply because their Michigan facility is about an hour from my house. So if it is stocked at the Michigan facility I can simply go and get it.
Depending on the item, I order some engine/tranny/performance stuff from the likes of Summit Racing and Jegs too.
Also depending on what you are ordering, sometimes it is better to order directly from their source suppliers to avoid possible mark ups. Some examples are interior pieces from Legendary Auto Interiors, convertible top parts of Hydro-E-Lectric., weather stripping from Steele Rubber products or Soft Seal.

Sure. You just need to find a chromer that can properly do metal, pot metal or plastic. However, it won't be cheap. Chroming seldom is cheap and what ever prep work is necessary is also usually by the hour as well. So do your homework and ask around.  Advanced Plating and Paul's Chrome are two nationally known chromers but I don't know if they can handle plastic or pot metal as easily. If your hood insert is cast or stamped metal, then any chromer should be able to chrome it. It if is pot metal or plastic, then a specialty chromer is needed.

I could be waaaay wrong on this but this is my first shot. So tell me what you think. I am not 100% certain that the brace is what is rusting or is it the windshield frame itself. The vinyl is definitely what you want once you've repaired the rust hole.
 
Upper windshield brace replacement 
https://www.opgi.com/sheet-metal-body-panels/windshield/1970-72-convertible-front-upper-windshield-brace9/brace-upper-windshield-1970-72-a-body-convertible-ch27796.html
 
Replacement Black Vinyl
https://www.opgi.com/convertible-tops-accessories/convertible-top-hardware/1968-72-convertible-header-panel-vinyl-strip/convertible-header-strip-1968-72-gm-a-body-black-vinyl-ch27567.html
True, and something like POR-15 will stop the rust. 
As I said before, it is the brace or is it the windshield frame itself. 
JustA has a point. Junkyards are an excellent source of replacement metal, especially in the Southwest. You want a 70-72 GM A-body convertible - Chevy, Pontiac, Olds, or Buick are all interchangeable for this purpose.

Check out Steele Rubber Products - they should have most of what you are looking for.
https://www.steelerubber.com/search?year=1961&make=pontiac&model=ventura&style=2-door-hardtop
 

You should be able to get a fuel to carb line off a Nova, Camaro, Monte Carlo, etc., anything that ran a 305, 307, 327, 350, or 400 2-bbl back in the day.

Hi David - welcome to FP.
The Pontiac 6000 is not supported very well by the aftermarket, I'm sure you know that. 
For cars that have little to no aftermarket / reproduction support, you have to rely on someone having what is called New Old Stock (NOS) parts - generally these are parts that GM produced as replacement parts back in the day (they are new - never used but old age-wse stock) or you have to purchased used/salvage parts from a donor car that is in good condition and you may have to do some re-conditioning yourself on them once you get them.
So general sources to look for NOS parts are:
eBay, Craigslist, Kijiji (Canada), local swap meets (not any of those going on right now sadly) and may be Amazon (sometimes you get lucky). There may be others but those are the major sources I would try first.
For donors, you have to check salvage/wrecking yards. You should check those in your local area if they have an 6000s and hope they are in good shape. Otherwise I have a list of wrecking yards I can recommend - they are generally in the southwest. However, I have no idea if they will have any 6000 parts since generally speaking, it is not a popular car for parts these days. These yards would probably have either the large cars or muscle cars from the 50s-70s in a lot of cases. That said, I will be happy to give a list if you are interested. 

Them's is fightin' words Chuck. Or at least sacrilegious to us Pontiac faithful. But I think you know that too!
There is a surprising a lot support for Pontiac engines, parts, etc.. Granted, it isn't as cheap  as "Cough cough" Chevy parts but it is there (except for the Pontiac 265 and 301 V8s). So if the issue is finding parts for your Pontiac engine, let us know. Yeah, we know that Pontiac parts are not as cheap as Chevy. That is not up to us. 
Now I have not done this swap. I will be honest with you right up front. However, I would start with looking at the motor mounts between the '65 Bonneville and the '65 Chevy Impala/Bel Air/Biscayne. I would expect the Impala lower motor mounts to bolt into the Bonneville chassis. I would start there. If it doesn't, then you have to fabricate your own.
A Chevy engine usually means a Chevy transmission because Buick-Olds-Pontiac (BOP) cars had the same engine-to-transmission bell housing bolt pattern. Chevy had it's own unique bolt pattern. You might be able to find an adapter kit. Either way, your original Pontiac transmission won't just bolt up to the Chevy motor directly. If you go to a different transmission, it is possible that you might end up going with a slightly longer transmission tail shaft, which means you might have to shorten your original driveshaft. Maybe. You may also have to move your transmission cross member back. If you do that, you may have to drill holes in the frame for the re-positioned cross member. You may need a different transmission mount if you end up with a different transmission. Again maybe.
The stock automatic transmission cooler lines may or may not fit your new transmission and radiator. So budget wise, be prepared to get a custom set made, or bend/build your own.
You might also have to be aware of how your emergency brake cable(s) gets run. When I upgraded from a 350TH to a 400TH in my '72 Lemans, even though the case length didn't change, I still had to get a custom E-brake cable made to re-route it around the relocated transmission cross member. Anyway, something to be mindful of. You may or may not have this particular issue.
Pontiac engine has the starter on the driver side. A Chevy engine has the starter on the passenger side. So you will need to re-route and lengthen all your battery cables - including those going to the ignition switch. Most Pontiac battery locations are on the driver's side - closest to the stock OEM starter.  
Pontiac alternator is typically on the driver side. Chevy alternator is usually on the passenger side. Again, wiring for the alternator made need to be extended.
Any engine swap means you will have to tweak your exhaust or build some sort of custom exhaust (in some fashion), regardless if you run the stock engine manifold or headers. Even if this is just adapting it into the current exhaust system on the car. 
If your new engine is significantly more powerful than your old engine, you need to consider upgrading your brakes. The more "go" you add, the more "whoo" you need to add to be safe. Stopping a 4500-5000 car like a Bonneville should not be discarded lightly.
Check your radiator. Will it work with your new motor? Obviously the stock hoses probably won't work. Do you need a new radiator just because the car is old? Again maybe. Regardless the radiator has to be matched to the motor and transmission. Does the engine fan/clutch/shroud now meet up correctly with the new motor or does that now need to be adjusted or custom made, etc.
That's all the obvious things I can think of at the moment. I'll let my colleagues on the forum speak up too, especially if I forgot anything.

If you have the money and the facilities at your disposal, a dyno tune is prefered over a remote tune. A skilled facility can adjust MAP settings on the fly based on the previous dyno pull results and fine tune your air/fuel ratio for optimum performance across the RPM range as well as make sure your oil pressure, o2 sensors, and other parameters are not out of whack. It will cost you more that a remote tune but it is hard to argue with the results.

Correct. PHS is the source for this kind of information

Hi Bernie - Welcome to FP. Carter and Pontiac had a 10-year run with Carter AFB carbs and lots of applications. Here is the list, as I know.  I hope this helps.
S/T = standard (manual) transmission
A/T = automatic transmission 
S/D or SD = Super Duty

1957 8 347 57-27, 57-28 Carter AFB 2506
1958 8 370 V-8 Carter AFB 2768 572
1958 8 370 V-8 Carter AFB 2751 572
1958 8 370 Carter AFB 2767 563
1958 8 370 V-8 Carter AFB 2740
1959 8 389 S/T Carter AFB 2820 563
1959 8 389 S/T Carter AFB 3123 586
1959 8 389 A/T Carter AFB 2819
1960 8 389 A/T Carter AFB 2976 563
1960 8 389 S/T Carter AFB 2975 563
1960 8 389 S/T Carter AFB 3123 586
1960 8 389 S/T Carter AFB 3010
1961 4 195 S/T Tempest Carter AFB 3266 .
1961 8 389 S/T Carter AFB 3123 586
1961 8 389 A/T 23, 25 Carter AFB 3125 586
1961 8 389 A/T 26, 27, 28 Carter AFB 3124
1962 8 389 A/T (4 speed) Carter AFB 3300 586
1962 8 389 A/T (3 speed) Carter AFB 3326 586
1962 8 389 S/T Carter AFB 3123
1962 8 421 SD (Rear of 2) Carter AFB 3435 558
1962 8 421 SD (Front of 2) Carter AFB 3433 558
1962 8 421 S/D Carter AFB 3444 550
1962 8 421 S/D Carter AFB 3443 578
1962 8 421 S/D Carter AFB 3596 550
1962 8 421 SD Tempest Carter AFB 3266 828
1963 8 326 S/T Tempest Carter AFB 3477 586
1963 8 326 A/T Tempest Carter AFB 3502 586
1963 8 389 A/T (4 speed) Carter AFB 3300 586
1963 8 389 A/T (3 speed) Carter AFB 3326 586
1963 8 389 S/T 28 Carter AFB 3479 586
1963 8 421 A/T Carter AFB 3545 549
1963 8 421 SD (Front of 2) Carter AFB 3433 558
1963 8 421 SD (Rear of 2) Carter AFB 3435 558
1963 8 421 Carter AFB 3443 578
1963 8 421 S/T Carter AFB 3574 586
1963 8 421 Carter AFB 3444 550
1963 8 421 S/D Carter AFB 3596 550
1963 8 421 Super Duty (3 barrel) Carter AFB 3636 591
1964 8 326 A/T Tempest Carter AFB 3687 586
1964 8 326 S/T Tempest Carter AFB 3686 586
1964 8 389 S/T Carter AFB 3647 586
1964 8 389 A/T GTO Carter AFB 3649 586
1964 8 389 A/T Carter AFB 3648 586
1964 8 421 A/T Carter AFB 3651 549
1964 8 421 S/T Carter AFB 3650 586
1965 8 326 S/T Tempest Carter AFB 3899 586
1965 8 326 A/T Tempest Carter AFB 3900 586
1965 8 389 A/T Carter AFB 3896 548
1965 8 389 S/T Carter AFB 3895 549
1965 8 421 S/T Carter AFB 3895 549
1965 8 421 A/T Carter AFB 3898 548
1966 8 326 A/T Tempest Carter AFB 4036 583
1966 8 326 A/T CA Carter AFB 4031 583
1966 8 326 S/T Tempest Carter AFB 4035 586
1966 8 389 S/T Carter AFB 4033 586
1966 8 389 A/T Carter AFB 4034 584
1966 8 389 A/T CA Carter AFB 4030 584
1966 8 389 S/T Carter AFB 4033 586
1966 8 389 S/T CA Carter AFB 4041 586
1966 8 421 S/T CA Carter AFB 4041 586
1966 8 421 A/T Carter AFB 4037 584
1967 8 326 S/T (CA) Carter AFB 4245 890
1967 8 326 S/T Carter AFB 4243 2205
1967 8 326 A/T (Tempest) Carter AFB 4246 870
1967 8 326 A/T (Tempest)(CA) Carter AFB 4248 891
1967 8 400 S/T (CA) Carter AFB 4245 890
1967 8 400 A/T (CA) Carter AFB 4244 891
1967 8 400 S/T Carter AFB 4243 2205
1967 8 400 A/T Carter AFB 4242 867
1967 8 400 A/T Carter AFB 4413 870

What is/was the cost of the upgrade when you did it? These are straight replacement  (modern - not NOS) T3 bulbs, not halogen or xenon, correct?
I just got the new 2018 National Parts Depot GTO/Tempest/Lemans catalog at the Detroit Autorama a couple of weeks ago. It's their first new GTO catalog in 3 years. On page 172, they offer both a T3-style halogen and T3-style xenon replacement. However you have to purchase 4 new t3 bulb-shaped relfectors to go with the H4 style halogen or xenon bulbs. So these bulb reflectors run around $75-105 a piece. The high or low beam H4 buibs are extra a $6-8 each. A complete set of T3 replacement bulbs cost $170 for all 4 bulbs, 2 low beams and 2 high beams.
NPD also offers a Halo LED head light set. What is not clear from the catalog is if this runs $195-250 per bulb (worst case pricing), a pair, or for all four. Of course this comes with a Xenon bulb and 21 LED halo ring that is color adjustable.
I have not checked out Original Parts Group (OPGI), YearOne, or Performance Years either.
However, you and I are both on the same page in regards to Superbad's question - yes there are options out there. Just not inexpensive ones.

Welcome Joe. As I am sure you are already aware, there is not much aftermarket support for the 73-77 Colonade style Lemans. So you need to rely on places like eBay, Craigslist, local swap meets, nation meets, or classic car wrecking yards.
 
I recommend contacting the following wrecking yards to see what they might have:
 
Desert Valley Auto Parts (DVAP) - home of the Desert Car Kings tv show
https://www.dvap.com/
East West Auto Parts Inc.
https://www.eastwestautoparts.com/
Frank's Pontiac Parts
http://www.frankspontiacparts.com/
 

Yes and no. It will physically bolt on but the 301 is a different size engine than all other mainstream Pontiac motors. It is a one inch smaller deck height, two main weight throws in the crank, and thinner walled bores. Basically Pontiac made the 301 and 265 to save weight. Bottom line it won't not bolt and fit up correctly to the 326-455 engines and heads. You should find a stock or aftermarket intake that fits your application.

With very little to go on, it appears to me to be a Pontiac Grand Prix GP or GTP somewhere between 2001-2008.  The headrest is what makes it appear to be a Grand Prix seat to me.