The Rears have 7.6" of backspacing stock, while the Z06 wheels have 8.8" of backspacing. That means that since the rears are currently 9.5" and the Z06 wheels are 12", they would stick out an additional 1.3" or so. Add to that the overhang of the tire sidewall, and you're looking at a fair amount protruding from the fender. You would really have to find Z06 style wheels for the car. You can space wheels out, but not in. C5 Z wheels have more backspacing, allowing the outside edge to be only 0.3" further out than the base C5 wheel (can't go all that much more without looking silly).