Changed from auto to 4-spd manual, then to 5-speed manual. Did not balance flywheel...did not need to. You can rev engine in neutral, or with clutch disengaged, to 4500+RPM w/no noticeable or unusual vibrations.
Here are some threads of mine regarding the conversion, vibrations and other fun:
Original conversion thread
Vibration 1
Observations
Dashpot
5-speed on the property