Larry Shepherd’ Mopar Small Block Engines book says keep mech fuel pump when adding electric.

I run an American made Carter P4594 electric pump along with an NOS Fram HPG-1 right off the tank. Fuel line from pickup to carb is 3/8”, no fuel delivery issues running the 1/4 mile at 114mph. I run a billet Holley regulator even though with that particular pump it’s not really required. The psi of those pumps show 5-9 psi, I can’t recall what psi I saw without the regulator but I had to dial in some regulation to keep it at about 5.5 or 6 IIRC. Depending on carb and electric pump you use you might not even need a regulator.