What is the size and type of bolt that goes into the harmonic balance (vibration damper)? This is for the six cylinder engine. My friend has a 57 "210" and the bolt disappeared, the the balancer (damper) is wobbling.
Also, was there a lock plate to keep this bolt from coming out?
Does anybody have for sale the little L shaped part that supports the air cleaner for this car?
Has anybody put a dry element into the oil bath type cleaner and used the oil?
Thanks.

There is no bolt. The balancer is driven on and is held on by friction. Perhaps the rubber between the hub and rim is "bad" and tha is causing the wobble.

Can you please tell me more about this rubber and how the balance is driver on and taken off? This is not my car and I don't have the shop book for this model. I have a 29 Chevy.

If the pulley is "wobbling" the damper needs to be replaced. It is a riveted unit. A balancer puller is used to remove it and then the new one is driven on.
I suggest your friend buy a shop manual for his car as he will find it very useful for working on it.