The roughest in the motor at 1800 to 2800 RPM in neutral may be in the carb going from the idle circuit only onto the transition circuits work scope
Put a dial back timing light on it and watch what the timing is doing, if it is all in before 2000 RPM it has to be some other part, carb maybe, causing that issue wrench scope
Personally I wouldn't worry much about it twocents work

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)