Lawman,
I am just going to throw this out there, Have you checked for a vacuum leak? The intake manifold at the cylinder head, Base of carb at the manifold? I would be reluctant to say, since it is a rochestor B carb, there are two screws that hold the base of the carb(where the throttle shaft is) to the fuel bowl part of the carb where the float is, that could be loose causing a vacuum leak. What is the idle set at? Where is the timing set, you can advance the timing a little bit and see if it makes a difference. Check for vacuum leaks with the engine running and some spray carb cleaner or a unlit propane torch around the intake manifold and the carb base.
Good luck. Some people will say I am off base with my thinking, But I have learned over the years to always check the easy things first.
