I realize this is a year old but for obsolete gaskets and seals, call these people up they specialize in remanufacturing no longer found seals and all auto both domestic and foreign as well as tractors and vintage tractors. If you can get a neoprene seal in lieu of a rope seal, do it. I have worked on a few inline stovebolts and found it is a great way to abate rear main leaks.
https://www.olsonsgaskets.com/
Steve