That's not really how that works. The fuel pump is providing(and rated for) a certain volume at a given pressure. The regulator is adjusting the pressure before the carb using a variable sized orifice and returning the unused fuel back to the tank. The pump impellers are designed to have maximum efficiency and volume at the pressure they are designed for. Any difference in the pressure of the system from designed would result in a lower than designed volume. The EP381 flows enough volume in a standard fuel injection setup ,with the regulator after the injectors, to support ~450hp. I would bet that having the regulator before the carb like that you will likely run out of volume much sooner than that. I would bet that setup runs out of fuel closer to 350-400hp(which would probably still put it near what you are going to get from the TBI pump).
It sounds like the OP is wanting to run serious HP, so he will likely need to swap to something a bit more serious, like a walbro 455 in the tank or a Holley blue pump on the frame rail. The holley blue would be comparable flow rating to the walbro, but rated at a more carb friendly pressure.