Lyman no longer offers the rebuild kits for the older small single cavity moulds, but they do have them for the later large block singles. By large block, think of single cavity muzzleloader moulds in 50 cal or so. I had to buy my replacement sprue plate from Red River Rick in Canada. Erik may have some, but the last I knew they were Ricks. BTW, they're excellent quality. As for the screws, there were also two different size screw heads between the newer and later designs. The heads on the later screws need to be turned down for use in older moulds. I believe the screw size & thread pitch remained the same though.