[ImperialCrown]

Any ammeter gauge needle deflection? Any test light action at the underdash fuse block?
An A-body wiring diagram may help you trace it out. This is electrically similar to the Dart and Valiant.

 

[ImperialCrown]

Headlights and courtesy lights wouldn't go through the ign. switch, but there may be a BATT (+) junction where the power is distributed from that could be the problem. It may be behind the ammeter gauge?
A digital voltmeter may still show 12 volts through a 1000 ohms of resistance (i.e.- loose, corroded, dirty, etc.), but that 1000 ohms resistance wouldn't allow the current through needed to light even a small bulb.
It is best to use an incandescent test light for these tests to actually 'load' the circuit under test.