I wouldn't use it on an engine that big. I just finished a 500 with the same specs exactly as my 451 and it made a little less HP & TQ. I think the next cam up in that series would work a little better. I think the 383 Six pack intake is too small, as well. When I put it on, I lost 1200 RPM on the top end from my old 383 Torker and an AVS.
However, if you're running a bigger intake, so it's not the choke point, I think the Stealth heads might be the next problem.
If you can get accurate flow data for your heads, Desktop Dyno will help with the cam and manifold choices. The actual dyno numbers were a little larger than the desktop numbers, by about 2 or 3 %. You have to ensure you're not trying to fool yourself with the computer program, it is accurate if you don't BS the input info.