SomeBeach... pretty cool stuff. I had a 40th GTP coupe, flipped it and have the 99s now. Had a 70 Skylark Custom HT, red. Have a 455 (Pontiac though, of course) in a 69 GP. Have one .45 and one Polytech M-14S. Great minds... have similar tastes I reckon.

Welcome aboard, man! Did a teardown on my 40th before scrapping, holler if you need any 40th coupe-specific interior stuff.

Since you have the Buick to feed your need, I wouldn't do much on the 40th other than make it so you like looking at it. Thats my approach and I like things that go bang lol. FWIW, never expect that GTP to hang curves like your full frame honey there does. They will lift a rear wheel if you yank the steering, then its over.