Regluar cooling water pump vs extra duty

[TurnNBurn]

Hello All Im in the process of building a 92 5.7 block for my 85 gmc. Im using 062 vortecs on it , and a summit intake. I using the brackets and stuff from the 95, and the roller valve train components from a 98 5.7 in the block, and a nice smaller howards hyd roller cam. I use the pickup for towing, wood hauler etc.. I went to get a new water pump and I was asked if I had the standard cooling or the extra duty cooling with a threaded port on top.

Can anyone enlighten me as to what is a extra duty pump. More flow? pickup has 4 core rad so i dont think it would be a bad thing or am I wrong

Does anyone have the pick of a extra duty cooling setup , so I know what I am looking at? Thanks All