Flywheel imbalance, 351W 4v

I just bought a 1969 M code Mach I (351W 4v) which was converted from A/T to toploader 4spd. The driveshaft wrung off and the tranny failed on the turnpike on the ride home, so I had a mechanic install a Kiesler TKO 500 5spd. He also installed a new Spec clutch and flywheel, and the engine has bad vibration when revved, even at a stop with the clutch disengaged. How can I tell if the flywheel I took out has the 28oz imbalance- is the imbalance the extra lobe cast into the flywheel in an apron shape just inboard of the friction surface? Maybe the Spec flywheel didn't have the imbalance required- can I add that through the bellhousing or does the tranny have to come out?

Any expertise or experience in this area is greatly appreciated.

All 351w's use a 28oz imbalance. Call your mechanic and see what he used. If it needs to be changed, the tranny will need to come out.

Update: My mechanic neglected to install the screw-on 28 oz. imbalance weight! Has anybody out there ever snuck one in through the starter hole in the bellhousing? That's my next challenge-who out there thinks I can git 'er done?

I believe that with enough determination and a bit of work you can do it. I would try if it was mine......
when I was younger and had a back that actually bent.....