holley 4150 carb issues and questions

Part throttle issues are primary side related. Give us the "numbers" you found during the rebuild. Carbs that old could have been modified/tuned many times over the years? Jet#, Nozzle#, Power valves, etc?

Do you have any idea what compression you actually have? A compression test would be helpful? Depending on those results, you may be able to hike your initial timing several degrees and that would surely help with drivability on the street or at the track.

You may not know what cam you have, but vacuum readings at a specific idle speed would help with diagnosing the tune.