Engine/drivetrain vibration?

Thanks again for all of the feedback. This situation keeps changing; my repair shop now thinks the new TC installed after the tranny rebuild might, indeed, be the correct one since it DID have weights. I think they were initially confused, since they probably didn't realize that earlier 340s had a forged crank (internally balanced) and thus should have had a different TC than the '73 version with a cast crank. This weighted TC was on the vehicle when the rebuild was done.

However, I suspect Locomotion may be right -- the problem may well lie with the balancing job done by the machine shop. If so, I guess the engine will have to be pulled and sent back to the machine shop for rebalancing -- correct? Is there any way to compensate for the balance problem with the engine still in the car?

Also, what's the long term implication of "living with" the vibration? Beside being a little annoying, will this condition shorten the engine life or cause other problems?

Sorry for all the uninformed questions, but I'm just a cosmetic restorer when it comes to these cars -- mechanics was never my strong suit!