Even though you have a hardened input shaft it may be off. I would do this. Pull the converter and tranny. Run the motor, if it shakes its in the motor. I bet you its either the converter or the tranny itself. I have ordered Nodular Iron cranks that were "Balanced" from the company that shipped it to me and when my machinist checked it the crank was waaaaay off. New parts can be bad and old parts can go bad when you put a new part on them..... don't ask me why.