If you don't mind using a electric fuel pump, Carter make a vane pump with a internal pressure relief valve that does not require a return line to the tank.
Pressure is set at 4 psi. The part number is P4070.
It also has the advantage of not supplying the fuel in pulses like the mechanical diaphragm does.
I have used this pump before with carbs and as a booster pump on efi systems and found it to be very reliable.
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