Did somebody say timing advance?
350/TH350, 700 RPM in Park, 550 in Drive. The 350 has a Comp 12-300-4 cam, which is a torquey cam, and that's with 16* BTDC base timing and a stock HEI.
I don't have problems maintaining voltage at that RPM since I put in a 94-amp 12SI alternator in place of the 43-amp 10SI. 12SI and 10SI alternators are same size, same brackets, same wiring, just swap it in.