The wiring schematics were in the 1963 Cadillac Shop Manual in the Body Chapter 16, Electrical Section as follows:
63-6267 Page 16-117, Fig 16-144
63-6367 Page 16-120, Fig 16-147
Note: the Body Wiring Circuit Diagrams, and the Rear Body Wiring Diagrams are not in the 1964 Shop Manual and you need the 1963 manual to refer to these specific schematics for the same body style. If you don't have a 1963 shop manual I have a good stash of originals for sale. Shoot me an email to email@example.com.