Have a 3rd gen firebird, just upgraded the rear to a 4th gen disc 3.42 posi. i knew this rear was longer from the sticky thread here talking about 10 bolts. however i cant find a "end all" answer for wheel dimensions and fitting the tallest, widest set up i can manage without serious tubbing.

Before the swap i was running 10.5x29.5 firestones on a 15" rim (not sure the offset) with minimal rub. i say minimal but they wouldnt fit at all without a little metal persuasion, also minimal. overall fitment was good.

the caliper to rim clearance on this swap is very small so i know ill be needing to go up a rim size. basically my question is what is the tallest widest tire i can run ? and what is the offset i should be looking at ?

 

I have stock late 90s Vette wheels on my car... 18x10 or thereabouts, w stock Vette size tires, can't recall the exact size. Fit fine w 2" spacers on a 3rd gen rear with no modifications whatsoever. Should fit the same on a 4th gen rear, or require at most a 3/8" spacer (since the 4th gen rear is 1-5/8" wider on each side).