I am getting ready to do a disc brake conversion, and had some questions. I realize that the 13" c5 vette brakes will never clear the 15" rally wheels, but what about the c4 12" conversion?? Any info on the topic is greatly appreciated!!

i don't know about rally wheels, but they do fit inside the 15X7 5 spoke 70-79 Z/28 wheels with about 1/8" clearance.