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
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