Consulting their tech support sounds like a good plan, especially before making any modifications. Maybe the solution is simple.
I've got an entirely different fuel pump strategy for mine. The fuel system is going to be the same as what I ran with the 383. The stock in-tank pump is capable of enough flow, but not when boost causes the manifold pressure referenced fuel pressure regulator to push fuel pressure to almost 70psi. The same set of Siemens 62# injectors I ran with the 383 is now on the 454. Using an external fuel pressure regulator instead of the stock GM one, the baseline fuel pressure is 3-bar instead of GM's 4-bar. That way, even with boost, fuel pressure never exceeds what the stock pump can handle. All this requires extensive tuning and a 2-bar MAP sensor to go with it. It's not a practical solution for anyone without access to a complete PCM tuning system. (I was not running Whipple's electronics with the 383, stock PCM handled all fuel - the 454 will be set up the same.)