it sounds like you may have a big rod 440 and need the external balanced damper... if the vibration is there just revving the engine then its SIMPLY an internal engine balance issue..if it does it driving only and pushing the clutch in doesnt affect it its SIMPLY a trans to rear end issue... i think you are so turned around from screwing with it you are confusing your self..so if its vibrating sitting in the driveway its the engine.. good luck dan