So, I am also a original owner delivered in New Jersey Avanti. From my experience dealers installed the mirror to the position that the customer chose, fender , door. I have never seen any order sheet that indicated to the factory to install a mirror in South Bend, but I am always willing to learn something new. My car had it's mirror installed by the dealer.
As far as one of nine 1964 R3 cars one was sold new in New Jersey and from what I recall it was a black car and I think that it was delivered in Vineland, New Jersey.