Magnum mount issue?

Hi Cory, how was it determined that your motor was externaly balanced??
Just by changing around dampers?
I bought a 70 Duster with a built 340 and many unknowns internaly. I thought all 340 motors were neutral/ internaly balanced with forged cranks.
My motor is a 340 with the internal style balancer on the nose of the crank.
I have some vibration issues and I want to get off on the right foot in regards to solving this problem. ie; type of damper,converter etc.
I have a converter that feels like it is in a out of balance condition, maybe the wrong one, or needs repair?