The pulley that is attached to the harmonic balanccer is damaged and needs to be replaced. I have a puller but am having problems getting the bolts that the puller pulls against started. Should these bolts be 3/8 or 5/16. This is on the original engine of a 55 3100. Any other general advice about replacing the pulley once I get the balancer off would be helpful. I think it is riveted on.