I have a 4 wheel disc upgrade kit for my 68 Firebird that comes with a front set of calipers off of a 73 Chevelle, and rear set off an 85 Cadillac. The front calipers fit fine. The problem I'm having is the rear rotors add about 1/4" thickness and I'd have to install 5/16" wheel spacers in order to clear the calipers with my 14" rally II wheels. If I add the spacers, it looks like I'm going to have tire rub since each rear wheel will now be mounted 9/16" closer to the lip of the quarter panel. Does anyone know of another option that will allow rear discs with a 14" wheel without having to use spacers? I think the wheel wells will take the wheels/tires with the additional 1/4" thickness from the rotors, it's the additional 5/16" from the spacers where I'm going to have the problem.