I'd suggest a smaller stroker (438) with a stable CH piston, Stealth/Eddy heads, Eddy RPM, higher compression at your altitude, a nice hyd. cam, 1-3/4" headers, 2-1/2 exhaust. Should have no problem hitting 450 HP. It's also do-able with stock displacement but you'd have to get a bit more aggressive with the choices.

I made about 560 HP (and left about 20-30 HP on the table) with my 383/451, but it's not a cruising combo.