We did two separate cars with 2.5" exhaust all the way out the back. One has OE wheelwells, the other was mini-tubbed with 335's on the back. I have yet to build a 3" but I do think it is possible. The first and second gen have about the same amount of room for running exhaust. I know you can do 2.5" and probably 3" on the second gen as well.

That car had 285's in the stock wheelwell. Our test car at the time of development had 335's on a 12" wheel (with a mini-tub). The car had a narrowed fuel tank and the tailpipes just had to run slightly different but 2.5" was still no problem.