The main thing to look for is 235 engine and 3/8 inch fan belt (1953-1955st).

I think the Hydra-Matic makes no difference to the 1953-55st water pump.
But, the Master Parts Manual says "except Automatic transmission" - I do not know why (Greg Hill or other H-M person might know). Maybe the PowerGlide 235 used a different water pump (maybe pulley diameter - I am guessing here).

I have a regular 1954 235 engine's water pump on my 1954 3100 Hydra-Matic engine.

CARDONE SELECT 5511510
AIRTEX AW108N ( they say "except Hydra-Matic" - maybe someone knows why?)