I just received my sport mirrors and Mustang II console and I what to install them on my '79 wagon. What's the best way to mount those mirrors? How many in/mm from what reference point(s)? I also want to know about mounting that console without colliding with the coin tray that's already there.

BTW, just dug up my old copies of my Clymer Pinto Manual and second edition of Petersen's Book of Pinto.

Tack welding the nuts to the door is one way to go-if you don't care about doing some paint reworking.  This would be more liable to be a really secure, permanent and non loosening method.

Another option is to use Riv-Nuts (I think they are called).  This is the same STYLE of nuts that the automakrs used originally.
These are fairly readily available. They work like a Pop rivet, and are installed with a standard rivet tool, but leave a hollow threaded barrel attached to the inside of the door. There is the possibility that the nut may be able to spin in place IF the nut is improperly installed in the first place, IF the attaching screw is overtightened, or IF it rusts in place and then it will be difficult to remove the screw later, without using a carbide bit to grind the head off.