Short water pump for 5.7 vortec.

[Chilly178]

I want to put a short water pump on a new 5.7 vortec that i'm gonna put in my 72 C20. The parts guy at gm said any short water pump would work, but i'm skeptical with the plastic timing chain cover a lot of people had fitment issues that I see online about having to change out or shave some bolts. I just want somthing that will bolt on without issues and will work with my original v belt pulleys that I want to use. I found one water pump that claims it is designed to fit over the cover its the https://www.summitracing.com/parts/edl-8810/overview/. A little expensive but if its made to fit then it might be worth it. The parts guy at GM showed me this waterpump and told me it would fit. https://www.summitracing.com/parts/nal-19168604 I see they are different pilot diameters too, can someone explain what the piliot diameter is and what one i will need for using orignal v belt pullies from a 72 350 and a standard rotation water pump on a newer 5.7 vortec (l31-r)? One guy in the revews of the gm water pump said their are two different lengths of short water pumps and that one is the longer one? I'm not sure what one would be the right application or what the short one even is. The parts guy was also pretty sure that my orignal manifolds would not fit even though some members on the board said they will. Any input on that? Thanks