Engine/drivetrain vibration?

At this point, we believe the machine shop balanced the engine like they would have done on an early (internally balanced) 340. We suspect they did not know the difference between the forged and cast crank motors (it would have been nice if they'd checked the crank before doing the balancing, huh?), and thus they did not factor in the torque converter weights as part of the balancing job. It appears they did have the damper on the engine when it was balanced, so now we just need to confirm whether the existing damper was for an internally or externally balanced engine.

As a side note, this damper has been on the engine for years (before the rebuild), and the car always ran fine -- so I have to believe the damper is correct for the '73 motor.

Assuming our assumption about the balancing job is correct (I say assumption, because the machine shop kept no records of the work they performed), then the use of a neutrally balanced damper with the B&M flexplate would make sense. I'll talk to my repair guy to see what he thinks.

Thanks guys, for all of your help!