That is going to take a lot of metal buildup to fill in those casting holes then drill and tap. Its not going to be a cheap repair regardless of how it is done and likely wont ever be as strong as the original. I think on that old tractor, best to just stop using the belly mount drawbar. You could get one of the fixed 3 point hitch attachments like folks use to put a ball on to pull a trailer with using the small CUT and pull what you needed from that