I just referenced some old build specs I have and I came across a CHP magazine (Jan. 2002, page 58) that had a chart that can "safely" put tires on most 1st gen Camaros and here is what they list as references. you can always go a little wider but these are safe for most applications


Fronts

Backspacing wheel width tire size

15" 3.75 7.0 225/55
16" 5.0 8.5 245/50
17" 5.0 8.5 255/40

Rears

15" 4.875 8.5 28x10.5 (which would be around a 245 or 255)
16" 5.5 8.5 255/50
17" 5.5 9.5 275/40

they didn't have a chart for 18" but I'm just trying to show you a baseline and the fact that the wider tire you use, the more backspacing you need. whenever I try to give advice on a forum, I try to be as clear as possible because I have seen people get so much wrong info and waste a lot of money.

if I have any doubts when I give people advice, I will let them know that instead of making them assume I am absolutely right