Ok, my new question is, do I want to replace my old large 110 plunger with the 120 version or the 91 version? My newer motor has the 120 version, but if the 91 version will work I think I'd prefer it since I wont need to worry about ever replacing the reg gasket. It appears that the reg gasket used in the 120 reg is only available in the $10 gasket set, and the 91 version doesn't use a gasket.

Will the 91 plunger and diaphram work in the 110? Any reason to chose the 120 version over the 91 version?

Kurt