I've had a pretty bad vibration in the engine from day one.
These nailheads are externally balanced and there isn't a pin in the crank to position the flywheel in only one spot. There is a locator hole in both the crank and flywheel.
I was 99% sure I mounted the flywheel correctly so I took the pressure plate to the place I bought it and they found it to be almost an ounce out, rebalanced it and the engine is smooth as silk.
I figured since the drive shaft was out I would change the 3.50 gears out to 2.75 and what a difference it made, I love them!!!!!!!!!!!!!!!!!!!!!!!!