Look at these two posts, start at the beginning of each. If your headlight connector looks anything like mine did you might need to replace the connector. ( I can help you with that if you need)
67 Dart Headlight Switch Demystified
67 Dart Headlight Switch and Connector Recommendations?
67 Dart Headlight Switch Demystified
67 Dart Headlight Switch and Connector Recommendations?
