My Bronco would randomly quit running (stall). Eventually determined it was ignition switch. Internal contacts had warn down enough (OEM part was only 50 years old) that in the run position with a little vibration they would open up, and engine would die.
Next time it stalls, DON'T touch key in ignition switch, pull over and stop, DONT touch key in ignition switch, open hood, and check voltage at distributor.