Top: MO-3032 12 (Bulge and multi holes)
Middle: M80-730 R 8 C Round shaped cavity OD 3.5”, ID 2 9/16” Hole ring dia 3 1/16” 1/4" NPT
Bottom: M118-276 3 C R (Different Design no boss C R/90 Clocking/Course Thread) Modified opening
Lever: 177-381 Lever Spring Gray 1.55”L x .390” Dia
Diaphm: None 364 Stud 2.20” OL stud, 8 hole 3 5/8” OD, 2 3/16” Lower Disc, 2 3/16” Upper Disc, Steel Spring

This was a pump with no date code, but the later manufacture with bulge on Top that marine pumps would have a vent installed. The Bottom was modified outlet to accept larger fitting by previous owner.

I did not cut off rivet to release spring and measure it.

The other portion of the diaphragm that effects volume and pressure of the pump is those steel disc that sandwich the rubber diaphragm. They are actually different diameters on original pumps depending on the model. They also have stamped ridge that had a patent by orig carter. If you think of the captured volume of fuel in the pump outlet chamber under the diaphragm when pulled up fully the size of that washer determines how much outside area of the diaphragm can actually stretch, tapered volume and what is solid surface for the built up fuel pressure to resist the downward push of the spring.
I have post picture of chamber before, here they are again. Notice gear shaped hemi chamber which increases volume under diagram per stroke, which also would lower pressure required to stop stroke when carb needle closed. Hence the larger spring force to compensate. I also have seen orig hemi with extra washers under the stud to increase preload of that specific spring. Also notice the bottom of the hemi pump does not have to have inlet fuel flow through a casting to get to chamber. The inlet fitting opens directly into the inlet chamber.

The round chamber is the typical 6903/4862/6270 modern pump parts.