According to Pontiac Master Parts Catalog dated 1960 and 1966 all Pontiac V8s from 1955 through 1962 (and a few newer ones) used the same water pump, part # 540069. While they don't have it listed for 1956 Pontiacs, RockAuto does have one for '62 Pontiacs here:
https://www.rockauto.com/en/moreinfo...350852&jsn=431
Don't fall into the trap of "reverse rotation" listed on some of these pumps.