shoulder belts for Daughters 65 Barracuda
I have a high mount brake lamp on my package shelf too. the after market kits come with a logic module that will keep the brake lamp from flashing with a turn signal.
I chose to route a wire from the brake lamp switch all the way back to the added lamp fixture instead ( no logic module required ).
2 points to mention... If the fixture is mounted inside the car it will need to fit snug to the glass or light will escape and obstruct the rear view.
Once a safety feature is added it must function properly to pass a safety inspection just as if it was original equipment.