According to my 67 dart wiring diagram there are no orange wires in the engine harness. Also the only black wires are the Alternator feed to the car (your black wire doesn't look heavy enough but the lug does look about the right side), negative coil to dist, front headlight low beam, which should be on driver's side inner fender.
Was the car original 383? Someone may have added wires.
The location of the orange wire would be about where the temp sender on a 273 would be.
