Since you mentioned it, I was messing around TC's site today. There are barrel specs there but, I don't know if they showed any chamber specs. You could get specs for it from a reloading manual by reversing the cartridge specs. I've heard of kits before, just haven't seen any for Contender. They just don't show up at guns shows. Good Luck
By the way, Graybeard is right, there are some grave safety concerns involved here. The little winchesters wouldn't be too terribly dangerous, it's just that folks get sued over that sort of thing.