Installing new mirrors on my 1971 Plymouth Roadrunner. I ran into the same problem with the mounting tab. I have a '72 Charger with an original remote mirror so I was able to spot the tab pushed through a hole about 3/4 of the way up the door almost under the upper hinge. First, remove both the upper and lower door panels as well as the chrome inside door handle and lock knob. Install the mirror and drape the remote cable on top of the window post; you can see if you look down the window track from the top. Second, reach your left arm inside the large opening at the bottom of the door grasp the tie and anchor tab and insert the tab into the hole. This will take some strength and long arms. But, it can be done and me and my son did it. Test it out a few times and then re-install the panels, handle, door lock cap and remote bezel. The threads on the bezel need to be carefully threaded to seat fully. Mine wanted to thread about 2 turns until I got it right then it mounted flush.
