No matter how good the two piece seal happens to be, do yourself a big favor and get the block machined for a Timken 417210 one piece lip seal, or the equivalent made by some other manufacturer- - - -Outside diameter 4 3/4", ID 3 7/8", thickness 3/8",double lip seal with a garter spring. It will also work with a speedy sleeve, since the garter spring can accommodate a .015" +/- shaft diameter.
If you want to load up your block and bring it to Townsend this year, I'll be glad to machine it for you. I offered to do a demo of the procedure at last year's show, but the promoter shot the idea down. This time, I'm planning to ignore anybody else, and machine somebody's block, even if I have to do it off site with an extension cord from someone's motel room, or a generator. I'll probably be bringing one of my own blocks, as I plan to build several engines with that type of seal in the near future.
www.ebay.com/itm/116927189289?Jerry