Wire colors, an ohmeter/ test light/ continuity checker and a FACTORY DIAGRAM are your best friends. If you have connectors/ terminals on some of the wires that can help eliminate some. Where does that part of the harness lay out? In other words is it lighting, wipers, or engine?
Unfortunately, MyMopar does not have either 63 Dodge or Plymouth manuals "over there."
EDIT I forgot to mention, MyMopar does have the aftermarket 2 page diagrams you can download. These are not as detailed and often leave out some details, but will get you started--and can be easier to read. I often use both