Nobody mentioned that you are 1-step ahead by having a 1965. That year and 1963 had bulkhead connectors with large buss-bars that feed the thick ALT and BAT wires thru. Dropping that in 1966 caused endless problems for those owners (i.e. "bulkhead melts" problem).
Thanks for posting that! That is what it kindof looked like in the photos but I wasn't sure. I looked at a non-factory wiring diagram for 65 at mymopar but don't fully trust those.
I'm going to post one more diagram with Shaun's voltage readings, and then call it a night. Car show/rally in the AM so probably won't check back here until the afternoon.