I had an old memory flashback while talking to a youngster of 50 @ a cruise night. He had acquired @ an obscene price, a 1970 Formula 400 Firebird. A very sharp Ride that Was much like my 1st new car, also a 70 Formula 400 when I was 21.  I’m sure anyone with any 70 Firebird who Perf’d it up & took to the track regularly caused the same issue. When he was restoring it he discovered crack under the paint from the top corner of the rear Window thru the body to the top rear of the door on pass. side but it was coming back & could be seen as a hairline crack starting again. I relived my experiences with mine including the same issue with mine in ‘71 when I repaired mine but didn’t get to the root of the problem. 400’s made a bunch of torque, too much for the new body design in 70 which looks sweet ( still love them ) but was too flexible for pushing the limits of the 400 engine. The sharp corners of the body @ the rear upper corner of door glass & rear window left a weak stress point under full torque loads on subframe & body in that area. He’d discovered the same issue I caused racing mine, although he didnt cause it as he didn’t race it as I had mine. At the time I’d tried the same fix, stitch welding the crack & broke most of the welds next few times I raced. I told him the real fix i found out a few years later was tying the front frame stubs to the rear near the rear spring shackles to make frame subframes more rigid. I didn’t do either as no kits were available @ the time & my funds $ @ 22 we’re thin 😂! I told him I wasn’t sure whether anyone ever made a kit for the ‘70 & newer Firebird & Camaro's but thought they must as 15 years later I had a Fox Body Mustang convertible with similar issues manifesting underneath that started showing hair line stress cracks where Sub frame & body met & found a subframe  kitl solving it & was sure if kit was made for the Mustangs they must have made for the Firebird & Camaro too. Fast Internet surf easily found one for him on the smart phone & only $185. It wasn’t that easy in the ‘70’s 🤔🤣. Pic included was mine in The Day, took a smart phone pic of an old glossy😁! Hope I didn’t bore you too much.

Interesting story for sure! Got a link to the kit? Might help someone who finds your story  

Subframe connector kits have been available for the 2nd-gen Camaros and Firebirds for awhile now. You can now also buy a complete custom frame for these cars, replacing the front and rear subframes if you'd like. It's a lot more money for sure, but they are available in the aftermarket, especially if you plan to do some form of racings, drifting, or auto cross.

😀My racing days are over, I / we, the guy @ the cruise night found a kit he liked almost Immediately on the Internet using our smart phone, still amazes me how easy all is now. Not so back in the Day😁! 
He decided on this one from Jegs https://www.jegs.com/i/Competition+Engineering/247/3113/10002/-1?gclid=EAIaIQobChMI6oyO2-ji8gIV3MizCh1jJATWEAQYAyABEgLCc_D_BwE

That’s great information tbone! 

I always thought to put the sub frame connectors under my 72 rs 

I did used to drag race her many years ago justA in sportsman class ... best it ever did was a 14.2 😀

2 hours ago, 64 kiwi boni said:

That’s great information tbone! 

I always thought to put the sub frame connectors under my 72 rs 

I did used to drag race her many years ago justA in sportsman class ... best it ever did was a 14.2 😀

Always had a blast @ the track. Early on in the late ‘60’s it was AADCO IN South Jersey near Phila. Later further North @ English Town near Trenton. My ‘70 Ram Air Formula ran pretty well. Consistently in the high 13’s @ 100 to 103 mph. They were ‘Happy Days’