[bobcowan]

Since it's there in all gears, it most likely not the trans, drive shaft, differential, tires, or suspension.

Did you put the dowel pins in the flywheel to locate the pressure plate?

Many billit flywheels have a removable weight, so you can use a 28oz, 50oz, or no weight at all. Did you check to make sure it matches with the rest of the engine?