Kelsey-Hayes disc brakes were available on A bodies from '65-'72. The disc brake specific parts were lower ball joints, spindles, bearings and seals, calipers, rotors, and brake hoses. The upper and lower control arms were the same for all brake applications (9" drums, 10" drums, discs). The only differences in the lower control arms occurred when the car was equipped with a sway bar or not, and that was the lack or presence of a sway bar tab on the control arm. If you still have the spindles, rotors, calipers, etc. then it may be cost effective to go that route. If not, you would be better off and money ahead to swap to the '73-'76 A body disc brakes. You will need upper control arms, spindles, bearings and seals, rotors, dust shields, calipers, lower ball joints, brake pads, and brake hoses. You will have much better parts availability for replacements later on and the initial buy in is less than finding the parts for a Kelsey-Hayes set up. The only draw back is the switch to 5 on 4 1/2" bolt circle from the 5 on 4" that you now have. The savings on the parts will more than likely pay for a new set of wheels. Just my $.02.
