disc brakes a-body swap

73+ A body is what you're looking for. I'd take the entire front setup if I were you (the 73+ is a MUCH better setup then the 72-), including K frame, brake booster, steering linkage, etc. Also just to point this out, 72- is a SBP of 5x4, while the 73+ disc brake stuff is BBP of 5x4.5