Well……I have used the NOS type Jetfire and Cutlass fuel pumps for years (almost 54 now). Have never had a fuel pump diaphragm problem. Recent (15 to 20 years) unleaded gas has alcohol added for octane boost and emission control. The best answer to have diaphragms resistance to these fuels is to have them made from fluoroelastomer material ie: Viton or Fluorel. However, my experience has shown that the standard rubber diaphragms from yesteryear work just fine, even for the long haul.
Want to be 110% safe, then rebuild with “alcohol resistant” or “modern fuel resistant” diaphragms.