The fishcap was standard on all 70 Cudas and a few early 71's. Probably just left over parts from 70. For the most part, all 71's were the plain cap without the fish. The plain cap was also the standard cap for all 70 and 71 Darts and 71 B-bodies with the rimblow. The Dodge cap was for both 70 and 71 Challengers and 70 B-bodies.
Dave