JMS rebuilt the stock oval-port cylinders using the original springs, valves, and retainers. The company did a valve job and replaced the valve stem seals. These heads are heavy. Get a friend to help if you can. If you’re on your own, a clever solution is to raise yourself up (standing on milk crates, in this case) to match the height of your engine stand so you aren’t lifting the heads up too high by yourself. By the way, we used the huge leather gloves to set the head on the block so we could wiggle our fingers out and position the head over the dowels. Once it was in place, we slipped the gloves out one at a time, avoiding scratching the gasket or sealing surfaces.