Good point Costello. Although I haven't seen a hard number, I would double the required flow (calculated by HP/12) to equal pump design limit at psi. This gives cushion for fuel filter and line restrictions...etc. The Carter flows 72 GPH @ 7 psi, so should be good to 450 hp with cushion.
Just as a point of interest (and to test my new picture hosting service http://free.***boat.net/ubb/smile.gif here's a chart with dyno data (compliments of MikeW) and Mallory fuel pump design limits:
http://users.lvcm.com/lvjetboy/FuelFlow.jpg
Hope the picture works
jer