1965 Dart Charging System Question

OK, I made a few more checks this morning. First, the battery is at least 6 years old, and I think it might be starting to get weak, although I haven't been driving the car a lot over the last week. Second, I'm not getting any significant voltage difference between the battery negative and ground, at least on firewall screws for the VR and starter relay (and block).

With the key on, engine off this morning, these were my readings:
Batt: 11.8V
Alt.: 11.4V
Upper Bulkhead (from splice): 11.4V
Lower Bulkhead (from starter relay): 11.6V
Starter Relay: 11.6V
VR Ign.: 11.1V

So I think the cable running to the starter relay could be changed, and there's definitely something under the dash going on. It's only losing .2V between the bulkhead connectors, but there's obviously something eating voltage before it gets to the VR, which is strange, because I changed that wiring yesterday (and it's better than it was). It looks like it might be the wire from the splice to the ignition switch itself.

I think I'm looking at an old car with old wiring here, and a bunch of small flaws are adding up. The probably answer is that I need to do some rewiring under the dash, so I'll put that on the eventual project list.