If the passenger door lock and ignition switch are original, you can take the door lock out (pull back the weatherstrip and pull the spring steel retainer out) and get the 4 digit key code off that. It's located near where the shaft that engages the door lock clips on to the lock cylinder. A locksmith can cut a key to match that code.
I bought a bunch of old keys from ebay and other sources and was able to match up keys to an ignition switch I had to be able to use it.
A locksmith can also pick the lock and find the key code stamped on the outside of the cylinder and cut a new key from that. The lock on an AD truck is easy to remove (two screws from the bottom of the dash, the three wires, and the light bulb socket snapped out is all it takes. The bracket will come out along with the switch.
If anyone would like to send me an ignition switch, I'd be happy to see if one of my keys will operate it (sometimes a different code will work), and get you the code off the cylinder.
