From looking at the specs, I'm thinking that it's a Crane H-278 cam. Yes, if you retard the cam timing it will raise the RPM level that the cam works best in, but, you'll lose low and midrange torque in the process. Crane grinds that cam with 5 degrees of advance built in and it works best that way. Mid range torque is far more useful than a few more HP right on top end. The valve float RPM is unaffected by the installed cam timing. I ran your combo through my Engine Analyzer program. I don't have a lot of your specs so I had to assume a few things. I assumd 1 5/8 x 32" long tube headers, with a very good 3" low restriction exhaust system, 9.5 compression, and standard 70's accessory drag. The computer predicted a peak HP of 382 at 5600 RPM and 409 ft/lbs at 4300 RPM. It predicted 250 ft/lbs at 2200, 300 ft/lbs at 2500 and 350 ft/lbs by 2900 RPM. It made over 390ft/lbs from 3600 to 5100 RPM. On top end it made over 370HP from 4800 to 5900 RPM and at 6000 the power was 365. That's a very nice flat power curve and would be dynamite with a 2600-2800 stall converter. That run was with the cam installed as it is ground, with 5 degrees of advance. It sounds like it might be exactly what you need.