I might go FI in 3-4 years so I will redo the entire fuel system then, for now I'm sticking with simplicity and going with a good basic pump (electric or mech) that will fill my needs. I should add it is a half filled block so the oil will run hotter and have been told that could make the mechanical fuel pump hotter as well, giving me more reason to run a return line.

I might go FI in 3-4 years

I must be missing something. The OP says he already has a holley 110 pump, Holley rates that pump @ 88GPH at 9 PSI. The op’s engine makes 500HP (corrected). When doing the MATH, that pump is more than enough (IMO). Let’s run the numbers. 500HP X .5 PPH / 6 (weight of fuel) = 41.66 GPH. Now having over 112% reserve seems like enough to me. And the OP will be running, for the most part, in air that is not as good as “corrected” air, so he will need even less fuel.

I am sorry but I went down this road once. I had a car making 675hp with a holley blue pump and was told “pump is too small, you NEED a bigger one”. I didn’t have a lot of money, so I skimped, saved and sat out some races until I could get one. After all that it didn’t make the car ANY faster, so now if the numbers don’t make sense, I don’t do it.

Joe

IMO this changes everything.

I would run an intank walbro style 340LPH pump and a regulator that will work at both carb and EFI pressures. A 340LPH pump will easily support 600 HP at EFI pressure, and will support 800+HP at carb pressure. The Aeromotive Phatom line is designed to go into a stock style tank, but a number of other companies have similar solutions. When you go to EFI, you will have to swap a spring in the regulator and hit the road...In tank pumps are quiet and stay cool. Do it once now and be set.

I always run a bypass return.