318 magnum vibration.

i put a 2000 model 318 magnum in my 65 cuda. Bought a flywheel and bellhousing off FABO. Have a vibration in the engine. At 3000 rpms it vibrates pretty bad. How can I tell if I have the wrong flywheel. Are there numbers on the flywheel. I’ve heard that 318 magnums are externally balanced.