Speaking of centerpins, if you are taking your leaf springs apart, get new ones. You can find new centerpins online, but finding them locally is often difficult. The old pins are usually rusted and just not safe for use. Also, since you are adding leafs, you will need a longer centerpin anyway. In a pinch, a decent hardware store will have grade 8 fine thread cap head bolts (top). Some light grinding on the head of the bolt until it tightly fits the spring perch hole may be needed.