i was thinking and its kinda late for me so it might be a stupid question, but if you swapped a 4th gen rear which is a little wider than a 3rd gen rear could you run a wheel with more backspace to make up for the wider rear? or is the difference in rear lengths not even big enough to take backspacing into account.

 

Yes, the difference in length is somewhat significant. About 4 inches total, or a little under 2 inches on each side. With a 4th gen rear you can run 4th gen offset wheels and I think C5 corvette wheels without any kind of spacer. See, 3rd gens and 4th gens had the same wheelbase, just the axle was wider and the wheels had more backspacing than 3rd gen wheels.