My '69 340 pulley has the offset hole. So did the old balancer. My aftermarket harmonic balancer, which is neutral balance for the forged 340 crank, has evenly spaced holes. I don't think you'll find any aftermarket balancers for either cast or forged cranks with the offset hole.
and that is a aftermarket "one size fits all" part. Same applies to a headlight switch. Replacement will have a tang for a ground wire whether your model has a wire to put there or not.
