'66 with a 2.73 in the rear?

[Rich 5150 69]

You have throttle linkage issues you need to resolve first, either your trans kickdown or throttle linkage has slop in it, or its binding up...then adjus idle speed in neutral or park, then set timming initial first / then vaccum dash pot, a small allen head wrench will slide into the dashpot turn clock wise to decrease advance which sounds like what it needs with manifold vaccum.