Since C bodies tended to come with the biggest brakes available I'm only going to cover drum to disc swaps. If disc were an option for your year C body then swapping those in from a donor would be the easiest route. Unfortunately, the older, mid 60's to earliy 70's, rotors are pricy. I have noticed that, for 58-64 C bodies, 73 B bodies use the same upper and lower ball joints. If the spindle heights are the same then I would suspect that any 73 and newer B body disc brake setup can be installed. I know for a fact that 79 Cordoba brakes fit my 64 300. I had to use the Cordoba's spindles, rotors, calipers, caliper adapters, and brake hoses. I did mount the spindles opposite to their respective sides. In other words I put the Cordoba's driver side spindle on the 300's passenger side. This was to allow fully turning ability, with the spindles mounted the other way the caliper would hit the strut rod. I also had to shorten the tie rod ends a bit in order to set the toe. A note of caution, if you have a single resevior master cylinder you must convert to the donor's dual resevior M/C. I used the 'Doba's proportioning valve and plumbed it myself. If you have an existing dual resevior M/C then you must either remove the residual pressure valvwe from the drum brake M/C or use a disc M/C.
.© 1996 Steve M. Knickerbocker