Pulled my 340 today VIN id? May belong to someone

It will be cast into the balancing lobe on the front of the harmonic balancer if it does. Not a big deal if it doesn't. It could have had a crank swap when it was rebuilt. If it does have the cast crank only harmonic balancer on it, the flywheel will be balanced specifically for that type engine too. Cast crank 340's were in production for a year and a half and all of them were externally balanced.