I have a 73 240z that has both a mechanical and electric fuel pump from the factory. I want to use the electric pump and delete the mechanical pump. Do I need a fuel pressure regulator or not, and how much cfm does the factory pump push. My motor has a healthy cam, 6 to1 header, and work needles in bell top SU carbs. All help is appreciated. Thanks

Why do you want to delete the mechanical fuel pump?

Why would you need a fuel pressure regulator? Are you planning on installing an aftermarket fuel pump?

Usually people delete the electric fuel pump after converting to an internally regulated alternator since the power for the fuel pump relay coil comes from between the alternator and the regulator.

If you retain teh factory electric pump you will not need a regulator. If you change to an aftermarket pump you might need a regulator depending on the pump you choose. Any pump with an output pressure in the 3 to 4 range and sufficient flow rate (volume) should be ok without a regulator. We are running a Holley Red pump (7 PSI output) with a regulator set to 3.5 PSI with good results, a bit noisy for a street car however.