Dart dash lights

Check your ground to the dash unit. It grounds through the mounting screws and not through a wire from the dash. You may wish to add a ground wire and see if that helps. If the dash voltage regulator was out, your gauges would not work but the lights still would if the proper ground was present. The gauges actually ground through the sending units so that may be why they still work. The high beam bulb actually has two traces to it on my 63 dash so I assume yours is the same. It will work without a ground to the dash as well.