do a search here and maybe on the PY board, on the water pump divider plate.
the clearence has to be just right, and i think the stamped impellor replacements have too much clearence and the plate has to be modified. The cast impellor replacements might be better. here is a website that goes over it. http://www.wallaceracing.com/water-pump-mods.php
several people here i think have had to do it, and might chime in.
