If you do have it powder coated make sure the guy knows to mask the seal/gasket surfaces, all threads, and "holes". Makes it easier to reassemble.

Overhaul kit would be Edelmann #7858. These are 30 years old, so you may have to do some searching. One online source for old stuff is A1 Cardone Auto parts, just do a google search it should come up. The last set of seals I got was from a Chev dealer, but that was 15 years ago, so while you may want to try, don't get your hopes up.

Also, in a town the size of Grand Rapids there should be a steering gear rebuilder, probably more than one. They do HD trucks, farm equipment, as well as automobiles, so sometimes it helps to check with shops that specialize in that type of equipment to get a lead.