you need the factory disc parts from a 65-73 C-body. 65-68 are nearly impossible to find parts for (rotors and calipers, and ball joints are even worse) 69-72 parts arent too difficult to find and are pretty cheap. the best upgrade, if you can find them, are the 1973 only disc setup..... basically the same as the 69-72, but the rotors are one piece instead of two, and are dirt cheap as they are the same rotors used on the B vans. Some late 72's had this setup too. I bought a march 1972 build date Fury to get the swap parts for my 66, and it had the 73 goodies. 69-72 are every bit as good, the only downside is the rotors are about $75 more EACH than the 73's
you can take your chances with aftermarket adapters. i wont take chances with the brakes.
BTW, the factory 73 front disc and rear 66 drum setup that's on my car now stops better than any car Ive ever driven....period! It's all factory parts or aftermarket replacement stuff (like ceramic replacement pads), new brake lines and hoses, and DOT5 fluid. nothing special.
