The Stovebolt Site Forums The Shop Area Engine Shop Vibration just off idle '57 235

I have a '57 Chevrolet 150 with a 235 and factory overdrive. It has a vibration just off of idle that I can't seem to pinpoint. It's fine at idle but just off of idle (my carb throttle shaft is warn and sometimes it idles a little fast until I punch the throttle) and at this faster idle it has a very noticeable vibration. Also, when I wind the car up in 3rd gear to get into overdrive the vibration is very present until I get into overdrive.

My suspicions are: Harmonic Balancer/crank/flywheel. Perhaps even an ignition miss, but I don't think a miss would cause the vibration I'm getting. I forgot to add that the crank and balancer has been drilled so that the balancer can be bolted on due to the keyway being worn.

What should I do to begin diagnosing this issue?

Thanks,
Brandon