I'd like to share my rear disk break experience. I use '78 Lincon Mark V calipers, caliper supports, rotors - the works. First it requires a big gearing rear end. The shafts must be turned down slightly and bearings removed. The caliper bracket slips on the shaft and a new bearing is then pressed on. The roters must be redrilled far a 5 on 5 1/2" bolt circle and the inside diameter turned larger (access to a lathe is helpful). Once this is completed, it is a bolt on setup.
Some spacing might be required to move the caliper toward the outside of the vehicle, 1/2" at maximum. A bearing retaining plate works well. The shock mounts will also have to be relocated inboard to clear the caliper. My costs are: $200 for calipers, caliper brackets, roters. $30 to redrill and turn rotors. New wheel bearings and relocating the shocks still left the total under $350, and they work great! I also use the master cylinder out of the Lincon with no proportioning valve or booster with no problems.