Turn Signal Issues 63 Valiant
I didn't realize you didn't have a manual or diagrams, good goin so far!!
You can download useable diagrams MyMopar:
These are not always entirely accurate, but a lot better than nothing
http://www.mymopar.com/downloads/1963/63ValiantA.jpg
http://www.mymopar.com/downloads/1963/63ValiantB.jpg
It appears that on your car? the battery feed and charging wire go through the bulkhead in separate feeds, so at least you don't have the typical bulkhead connector problem, I'm guessing, or at least they should be easier to repair.
Here's a 66 shop manual, but I don't know how close the wiring will be, so be careful:
http://www.mymopar.com/downloads/servicemanuals/1966_Plymouth_Service_Manual.zip
This manual does not follow the "dash" page numbering system as it should in your reader, so you'll have to play with page numbers
Electrical (chapter eight) starts page 189, and wiring diagram index page 289