I have replaced the water pump on my M35 B with an Oberdorfer for ease of impeller change. There was no problem with the Sherwood when I did this. Included are 2 impeller kits and a quick disconnect assembly for the hose to make belt changes easier.
All for $275 plus freight.
contact Kent at kjoverbeck@epbfi.comhttp://c34.org/bbs/Smileys/default/icon_clap.gif
Kent - why don't you keep the Sherwood as a backup? I know the Oberdorfers are much easier to service, but I still think it's easier to swap the whole pump if something goes wrong at the Worst Possible Time than it is to pull them apart.