Jim Sewell raises a very good point in his post about domed pistons and water pump changes, which fits right in to the thread
http://www.mapleleafup.org/forums/sh...ad.php?t=12592 (I'll post the piston listing pages on that thread.)
As to the water pump the picture below shows a `41 style water pump single inlet and the later 2 inlet + vent of the second style as you can see these are not interchangeable. This becomes very evident in the second photo which shows the gasket for two hole on the `41 single hole, as you can see the inlets don't line up nor do the mounting bolts.