So this story is 2 1/2 years in the making, not that it was hard or took time to do - we're just slackers and needed some additional motivation. Simply put we bought the NOS mirror and it took that long...
The previous owner (Really thought we were done talking about this guy) needed a side mirror and since the car was found without one - well he took some liberties.
We don't know what the mirror was from but it had the little control stick/adjustment mounted in his make shift door card. As part of the upholstery upgrade we removed said control and cut the cables to the mirror, which immediately flopped down. "Well ^&*$" was our collective statement. As we did not cherish the thought of opening the door up we simply took the mirror apart and fabricated a mount for a small convex mirror that may or may not have been "legal"‽ (interrobang for the win)
This was meant to be temporary and it was for about 2 1/2 years.
So now we are prepping to replace the door glass and windshields so it was time to finally use the NOS mirror, (which is just awesome)! Of course we had to remove the previous mirror base and found the original mount (Read as jagged hole) along with the previous owners holes. We purchased our replacement mirror based on the mount length which hopefully would cover all of the holes. My finger is showing where a new hole is needed to mount the NOS mirror. The far right hole, from the previous mirror, is used for the rear most bolt of the NOS mirror.
And it does. 
As a foreshadow - this step was needed as we need to have the California Highway Patrol verify this is a 1950 and we don't need a ticket for an invalid side mirror while we are there. Currently the California DMV believes the Chevybaker is a 1948. We blame the previous owner. :)