Wiring Issue

1965 Dart Convertible GT. My tail lights were going on and off. Adjusted bulbs etc. working fine now but headlights went out. Any advice?
The headlights are on a seperate circuit from the tail lights.
They do share the 'headlight switch' but inside the switch the circuits are seperate.

Don't know what you mean by adjusted bulbs, but that should not effect the headlights.
The tail lights use 1034 dual filament bulbs that only fit correctly one way.

I would do these checks to narrow down the problem area.
You can do these with the engine running or the engine off.
Doing it with the engine running keeps the battery from getting run down and provides electricity at 14 V.
Doing it with the engine off allows you to check the ammeter for the amount of current getting drawn by the lamps being turned on.

1. Briefly step on brake pedal, both brake lights should turn on.
2. Turn on parking lights. Front markers and rear tail lights should turn on. Instrument lights should turn on.
3. Turn on on headlights. Front markers should turn off and headlights should turn on.