Balance Issue

I purchased a crate engine that is internally balanced. I have the balance specs and everything apears fine. I installed a harmonic balancer and flywheel which were specified for internal balance. At 3000 RPM I have huge vibration issue in neutral and run up. Any ideas? its a 496.

i would say it is external balance specs will not tell you any thing if external the mass wounld have been spun with damper and wheel so something is off