A-body SBP 8 3/4 brake backing plates
4 wheel drum brakes have 2 1/2 shoes on all 4 wheels. Disc brake has 1 3/4 shoes on the rear.
Please note that I see 70 Dart Swinger engine bay photos with drum brake master cylinders on them even though every 70 340 car has disc brakes on the front, standard! This is why people are unfamiliar with cars that they have purchased with these items on them.