I use to use a Holley blue 110 GPH electric pump between the tank and the Carter 3 valve NASCAR mechanical fuel pump on the motor without a regulator on my old NHRA 426 C.I. Max Wedge Stocker. The mechanical fuel pump will and does act as a pressure regulator My message is don't waste your time and money on a regulator now before trying that electric pump working in series with your mechanical pump A 1/2 inch O.D., 7/16 I.D. line, is fine as far as I've used for motors up to 700+ HP My new drag car will have a 5/8 O.D., #10 AN size, hardline from the pump to the pressure reg. mounted up front in front of the carb. due to shooting for 850 +HP carbureted now with EFI in the potential future for more power with a power adder later. I'll use #12 AN from the tank to the 500 GPH electric pump to start with, over build it once instead of doing it twice BTW, how many GPH is that Holley black pump rated at