That was my first thought too. That flasher can be really hard to find. It is on the drivers's side up under the dash, near the vent if I recall.After re-reading your post, I think I understand that the parking lights and the tail light turn signals "blink" when you switch on the hazards? Do you realize that your car (66 Mustang) has TWO flashers? One for the turn signals and another for the hazard lights. Your turn signal flasher could still be the root of your problem.