Fuel pump replacement

Good evening to everyone.  I hope someone can chime in.

I  have a 46 Ercoupe 415-c with a C85-12 engine.  My fuel pump diaphragm started to leak so I have to buy an overhauled Fuel Pump.  My question is:  currently installed is a C75 Fuel pump according to the stamped number on the pump installed on my Ercoupe.   Should I replace the pump with what I have installed or replace it with the correct Fuel pump for my engine?  The C75 Fuel pump currently installed on my plane says it has 5-7PSI and the C85 Fuel pump has 3.5-4.5 PSI.

I don't know if the current pump installed on my plane, although stamped says it's for a C75 has or hasn't been rebuilt to be for a C85-12 engine.  The arm's are the same for the C75 and C85 so I understand. 

Anyone have experience or first hand knowledge on this subject?  Greatly appreciate it and look forward to your responses. 


Blue Skies,
Dennis