you should drive it and see what you have before you start getting into it. there might be a vibration that changes under load with the transmission engaged.
there are many things that can be suspect. the balancer, flywheel, torque converter, driveshaft, yoke.
and the 3rd member yoke.
easy things you can try.
first drive the car and see what you have with the current setup.
if you find vibration you cannot live with.
1) mark the position of the driveshaft on the yoke and the 3rd member.
flip the driveshaft on the 3rd member yoke 180.
retest the car see if something changed for the better, if not you can flip the transmission yoke 180 and reinstall. retest the car again.
there are 4 possible combinations with the driveshaft that can reduce or eliminate vibration.
if nothing worked then you go deeper, flywheel, torque converter, balancer, you can have the drive shaft and yoke checked for balance as well.
sometimes driving the car for a while loosens everything up and a vibration can reduce or go away.