yes '73-'76 A body front disc apps were all BBP (single piston calipers) but '73-76 A body front drum brake cars were still SBP, at least some were (I've had several). not sure if any 4 wheel drum 73-76 A setups were BBP.
disc only were 4 1/2". drum brakes were ALL 4" bolt pattern. those cars were relatively new back when i owned a junk yard. we had hundreds of then through during 72-84 and ALL the A body drum cars to '76 were 4" bolt pattern.
