Ebay's got body service manuals for 75 Dusters. They aren't free, but it'll have every wiring diagram you need in it. Mymopar has them for 73's, so if it's close enough, you can get that one for free.
There are two volumes, body and chassis. Traditionally, the chassis manual has the complete diagrams, not the body manual. You really need both to have a "complete" manual
