No Brake Lights 1969 Dart(Different than post underneath)

People hesitate to accept the diagnosis. Not because they can't comprehend the circuitry but because the signal switch costs 60.00 or more and it takes half a tool box to change the darn thing.
Try working in a service center and quoting 150.00 to get Joe Customers brake lights on. Often times Joe had stopped in for just the annual 3 dollar safety inspection sticker and didn't even know his brake lights weren't working.
For what its worth this is common to everything American made for many years. Good luck