The big issue with the O.S. pumps is replacement parts. You can't get parts for 120 surpass II pumper now. Neither pump or regulator. The regulator is the biggest issue as it means a full carb replacement if the diaphram goes. If the pump goes, you could go with an aftermarket I'm guessing, but the regulator is an issue. One that I found out after buying a used Surpass II and then found I couldn't get parts for it. I've been trying to find out if the III unpumped carb will fit, but I think the answer is no.

Don