Charlie,

Contgrats on removing and replacing what most be one of the more difficult parts. We replaced my freshwater pump this spring. I think it was part of the original equipment, and I figured it was going to be replaced at some point, might as well be while Discoverie as on dry land. I have the W58, link included for reference

for the 63B four and the 63C four they list this: Westerbeke, Pump, Fresh Water, 32213, 032213

 http://discountmarinesource.com/p-3401-westerbeke-pump-fresh-water-32213-032213.aspx

you might give Discount Marine a call, they have a good collections of Westerbeke parts and might be able to confirm.

in case anyone is looking for the W58 part, we installed this: 

tkx,

rb