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.

I had to upgrade my rims to 15 inch when I did my upgrade...

Roll your fender lip. You might get enough clearance. We used to use a baseball bat. Man, how old am I? Lol.

I agree with jman01, using those calipers the 15s are the way to go. added benefit is you now have more tire options with the 15" tires. With 215 tires on mine there is little to no room for a spacer