From 1973 to 1975, the A body disc brakes were the same from the ball joints to the calipers. Sometime in 1976, they changed to a different caliper with a larger bore size. the 73-75 has 2.6" calipers, the 1976 models used a 2.75 size. The larger bore size provides more stopping power with the same pedal effort. I have these 2.75 calipers on the Charger. I also have a stock type 1975 Dart master cylinder and brake booster.
I always remove the thin metal splash shields when I work on these setups. They retain heat. I don't need them for protection from the elements because I don't drive my cars on gravel roads.