11.5V = Dead Cell?

Get into a service manual, that is maybe go to MyMopar and download the 67 manual, and in section 8, electrical, pay attention to the procedure to measure alternator field current. I'm thinking the rotor is partially shorted, drawing too much current.

One of the first things you should do is either swap in a known good battery, or yank out the one in there and charge it on a good charger, then let it set for at least an hour and have it load tested with a carbon pile tester.