What does the internal mounting structure on a 72 side rear view mirror look like? I removed my mirror and found that someone previously had used a larger screw to mount the mirror bracket. I bought the correct bolts for that bracket but they are smaller. I was wondering by using the larger screw that it has stripped the internal mounting of the bracket?

Not sure if yours is the same as my 73 but it used Well-Nuts to mount the brackets to the doors.  Well-Nuts are like a threaded insert with a compressible rubber piece in between the two pieces.

This is the kit that I bought. Do the weld-nuts install from the inside out with the wider end inboard position inside the door structure?

The Well- Nuts ate inserted small end first into the hole. The back and swell up against the inside surface of the door when the screw is tightened.

So it is inserted small end first into the hole from the inside of the door out? 

You insert the Well-Nut from the outside of the car. You put the bracket on top of it, insert the screw, and thread it in and as you tighten the screw, it pulls the threaded portion that's inside the door panel back towards the outside causing the rubber to swell up bigger than the hole. Since you mentioned that your whole it's bigger than normal, you may have to buy a slightly larger Well-Nut than stock.

Really appreciate it!

An alternate method is to use Heli-Coil threaded inserts; to be able to use the original size & type of bolts.

I don't think a Heli-coil will work very well in a fiberglass door.  ;)

I agree, Helicoil is a No Go.