Chuck,
Not to dispute you but we just went through this with another 318 and we even tried different flywheels and no luck. So we took it apart and balanced the assembly, with the dampner and flywheel we even bolted together the pressure plate and clutch disc. on the crank, and it was a good bit out we took 66 grms out of the rear part of the crank. Then after we reassembled the engine it was smooth as silk and its been running for a few months now as a DD.