Power Steering pumps ?'s

[ck5566]

I am going from a Non Power Steering Truck and putting on Power Steering now. I am going to probably re build one of my two Prw. Strg Pumps that I just recently acquired and I would like to know how to tell if one of them is a OEM pump or aftermarket? Do the pumps have any numbers anywhere on them or any identifying marks? My two pumps are still dirty/greasy. I also have seen that there is a Eaton pump & a Saginaw pump, how do you tell which one is which? Pictures would be good. When I clean them up and paint them I will post some Pictures. Thanks in advance