I believe a 9.5" wide C5 wheel has the same backspace as a 9.5" wide 88-96 C4 wheel.
That being the case, bolt-on spacers for 84-87 cars should be 3/4" thick. 88-96 cars wont need spacers, the wheels will bolt staight up.
if doing 4 fronts u can get by without spacers. to use the stagged set i used 1.5" on the rears and need a .75 for the front to look rt. cant find a .75 though....oh i have c6 wheels but they the same i pretty sure
I just mounted some 2000 z06 wheels to my 95 coupe. I was pulling hair wondering which spacers to use after reading all the threads. I just bolted them on and they sit as perfect as did the sawblades. No Problems.