The Victor EFI intakes have an advertised operating range of 4000-8000rpm out of the box... I think the Victor EFI manifolds will support 700hp. easily. Short runner intakes with LARGE cross-sectional ports...
There are some modified hyd. rollers that are spun to 8000+rpms... I spin mine to 7000 (Victor EFI intake w/ two 1" spacers) and pull a gear no prob. AFM sells a hyd. roller cam that is claimed to be good to 8600 with Ti valves, 10* locks and retainers, and STOCK hyd. roller lifters... I run Ti locks and retainers, but WHOA! the Ti. valves are out of the budgie.
Overall, I'm pleased w/ my Victor 5.0 intake, and I plan to use it on the solid roller R-block 331 I have planned for this winter's project... of course I'm going to ditch the spacers and clean-up the ports some... I don't have any experience with carb-to-EFI intakes, but obviously they work pretty good on some of the Big Dog's rides that make well over 1500hp...
I'll have to settle for just 575-600hp for now...