Let me go through this one more time for you. Not sure what you are asking here about the water pump. In #28 you asked if the water pump is a bigger diameter than the bottom port on the radiator. Me personally I have never seen a radiator that has a bigger port on top than the bottom. The water pump size should be the same size as the top port on the radiator as the hose connect to each other. the ID of the top port and the ID of the top hose is 1 1/2". The bottom port of the radiator is 1 3/4" in diameter as does the ID of the bottom hose. At least this is the size of this radiator, this hose and this water pump. I may have an orphan here. Hope this helps.