I have one of these VERY VERY hard to find locks that were made specially for the 47-55 under bed spare tire carrier. The key is the same type as the ignition and glovebox. Try another locksmith, then another until you get the guy who knows what to do. Do not mess up that lock!! Its like gold. I'm not sure $1000 would be enough to sell it.
Those who had them back in the day hated them to a purple passion. Why? Imagine a rear flat. Not only can you not get to the spare tire, but now you have a lock that has had mud and crud slinged all over it for years. By the time you have lost your head, over-handed the spare tire carrier lock out into the field, tossed the spare tire carrier in the ditch and threw the bad tire in the bed, you never looked back. So, if you can find them, its with a metal detector in the field, or ebay or the like and I havent seen them in years.
Home page here has a pic of what he is talking about:
www.devestechnet.com
