repair of 66 Barracuda Fender mounted Turn Signal Fins

Just the centering pin is broken? If you really need it, I'd drill a hole where the pin would be and install a roll pin.
Yeah, it just broke off at the base. The thought was to drill and pin, but it may need something to solidify it as the pin hooks on the small forward hole int he fender. It is this stress that makes me doubt that the fix will work, long term, but I will try it.