It seems like there are at least 3 water pumps for Y's. The above mentioned '54 which seems to have a different flange and impeller is one. Then there are 2 pumps that will bolt on to the later timing chain covers but have different casting and shaft diameter. The heavy duty truck pump had a thicker shaft, bigger bearings and cast on gussets on the supporting snout. The pass car pully will not fit over the shaft.

The HD truck is the new one. The rusty one is the pass car, light truck and T bird pump, these apps are interchangable.
Doug T
The Highlands, Louisville, Ky.
