I am by no means an expert on these, but Cardone seems to able to rebuild ANY water pump - like if you have one from a Ruxton. Technically is isn't that hard. You need seals, maybe a new or resurfaced shaft, and the hardest part, possibly an impeller. None of these are insurmountable - even for hobby machinists.
Outfits like Cardone have a staggering water pump parts inventory with which to work.