Balance Problems...Vibration......

I have to believe its a balance thing. did it start after puting it together? Does it vibrate bad out of gear reving it thru the RPM range or just in gear moving?

1.) Did it start after any part was chanced?
2.) need to make sure you have the right balancer on it along with...
3.) the right Torque/Stall Converter (for your forged/cast crank)

I had a 73, 340 with 4 speed that was built before I bought it. Had the vibration when I bought it (great price) and thought it would be just a matter of swapping out the wrong balancer. Turned out it had the right balancer, but a Flywheel for a "forged" crank. Had to find one for a late 72, or all of 73 340. It has a cut out on the face of the flywheel for balancing it.