I just measured the mirrors on my 73 Challenger. I've owned the car since it was 6 mos. old, so I know the history on the car. It has the original doors & skins. Car came equipped with dual chrome sport mirrors, which I've replaced with painted sport mirrors, using the original screw hole mounts.

From the front leading edge of the door to the centerpoint of the front screw, both mirrors measure 15 3/4".

From the top edge of the door to the front screw centerpoint, the drivers side measures 7/8", and the passenger side measures 3/4".