Oh, I am very familiar with flat tappet - lol. Vr1 - quick and easy to get. almost bought yours, but did not.
Update:
Removed accessory drive pully - still vibration.
Removed Harmonic Balancer - found a PN............. 3614369 - which according to Mr. Google, this is an internally balanced 318/340 Harmonic balancer...... wonderful.
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I am in need of that balancer now - I will PM you.
Pulley is from a 73 340 - so should be good.
Thanks