now that I have updated my distributor  to HEI and rebuilt carb and time to change my spark plugs. Should I stay with the standard plug that it use to run on or is there a better plug I could use for better running and gas mileage.

I run a breakerless Pertronix II in my stock non-HEI distributor with stock AC R45TS spark plugs. As long as I keep the engine tuned up properly, I have no problem running the stock plugs. Back in the days of leaded gasoline, you use to have change those plugs every 10,000 miles. Now I've run the same set of plugs for over 40,000 miles, which is about 10 years of linear time. 

You can upgrade to platinum or iridium plugs if you'd like. It comes down to a combination of cost, personal preference, and peace of mind. Some people feel the E3 plugs enhance mileage. I personally didn't have any luck with the E3s in my '04 Avalanche.

Since I drive Lucy less than 5,000 miles a year (last year was under 100 thanks to COVID), I am not very concerned about MPG. Unless I am driving cross country in her, I don't even keep track of MPG. These cars were not designed for mileage by today's standards. So unless I was going full on fuel injection, installed an overdrive transmission, and highway gears in the differential, I am not going to worry about MPG. Lucy gets 8 MPG with the top down period. I've gotten a best of 14 MPG highway with the top and windows up.  I have a 455 with TH400 and a 3.55 rear.

In my opinion, a '69 Bonneville convertible with a 428 is not a machine to worry much about MPG. If you are like me, you bought it to cruise around with the top down. 

Hey Frosty hope your staying healthy your right only get so many mpg's was just thinking of getting it to stay running smoothly. Got the engine running pretty good and the interior is now complete except for the carpet .Only problem now is my gas gage.  Had two rebuilt one I bought and the orginal one but they said there is something wrong with it had it checked again the guy that rebuilt bench tested and said it was good.The gage itself tested good and they said it must be short somewhere but nobody there knew how to chase it down.Even bought a new lead wire so the hunt goes on to find a wire guy

So far I'm managing to hang in there. Like everyone else, I am going stir crazy hanging around the house all the time.

A stock spark plug will do the job just fine as long as you keep your engine tuned up Terry.

Can you explain your gas gage issue in a little more detail? Is it not reading anything, partial full?

yes Frosty it went from empty to a little over 1/4 full. not really sure where the short would be at if the gage works and the sending unit works when bench testing it. Would be nice to have is all.When I had the dash off and repainted and stuff I got my heater to work lol..Won't be long and we can fire them up and break the cabin fever.Had the carb all dialed in and timed Runs a little rough when cold but it's been around 25 here but settles down as it warms up

4 hours ago, TerryH said:

yes Frosty it went from empty to a little over 1/4 full. not really sure where the short would be at if the gage works and the sending unit works when bench testing it. Would be nice to have is all.When I had the dash off and repainted and stuff I got my heater to work lol..Won't be long and we can fire them up and break the cabin fever.Had the carb all dialed in and timed Runs a little rough when cold but it's been around 25 here but settles down as it warms up

Terry check that your sender unit has a good earth, and a simple test to do is the one wire that goes to the sender unit, earth it at the tank end,and see what your gauge is reading, it should jump straight to full, if it doesnt there is a issue with either the wire from the gauge too the sender or the gauge itself has a fault.

Then the next step is to find on the back of your gauge the wire to the tank and earth that point out. if the gauge jumps to full, the fault is in the wire. if it doesnt, its a fault in your Gauge.

one thing i would ask is what was the range in ohms when you tested the fuel sender unit, i think gm are 0-90 ohms??? not sure, one of the guys here would know.

Generally speaking, 0-90 ohms was the GM standard.

Terry did you go from points to HEI ? the gap of the plug should be increased if that's the case.

yes I did how much more or less of a gap should it be?

i run a 45 gap on my car. seemed to be the consensus when i went to HEI. supposedly its a hotter spark because of the bigger gap. which will change the timing sequence so you may have to experiment. My engine liked the change but i did'nt dyno the changes. Justa something to think about ( or in my case obsess over) . chasing power is a never ending game. Learn how to read your plugs (i'm learning daily) as thats a good indicator of where ya want to be.

The stock non-HEI plug gap is .035. Most HEI or MSD electronic ignition have plug gaps that are either .040 or .045. So Indymanjoe' .045 gap is within spec.