Are you talking front or rear? I've got 16x9.5" rims all around on my '96 Z-28. The rims have 6.75" backspacing, and clear everything. In front, upper a-arm clearance would probably be your first concern. In the rear, either e-brake, trailing arm, or inner fenders would be close.
See the stickies at the top of this forum. There is a lot of useful info in there. Especially with respect to this question. One guy has created a wheel chart to give you an idea of where the wheel will end up widthwise. Very useful.
im looking to go wih the torque trust II's, my fav rims, i may be able to get a great deal on a set of rear rims that are 18" by 10" with a 7.25 (not 7.5" my mistake) backspace!
just wanted to know if there would be any probs...