While I have yet to actually rebuild one of these pumps, I have given it considerable thought on how I would do it. The original diaphragm (#11 in the diagram) is actually two sheets of material with a brass rivet holding the two sheets together. Spring (#12) rides against the rounded head of the rivet so it does not wear through the diaphragm material. I guess you could find a modern equivalent of that brass rivet but I’m not sure how well it would work.
My plan when I do this project will be to use a single sheet of diaphragm material and separate the brass rivet from the old diaphragm and then solder it to the spring (#12) so there is a smooth surface riding against the new diaphragm.
Knock on wood, I personally have not yet found one of these fuel pumps in non functional condition, and I’ve been through over a dozen of this style. They all seem to pump just fine and I use regular ethanol pump fuel but I always run the motor dry before storage and keep the fuel fresh.
The holes for the screws don’t have to be as perfect as you think, as long as the gasket openings where air and fuel are moving through are pretty precise, just take a big needle and poke a hole through for the screws and call it good.
.
