Hello Steven,
Happy Holidays to you and your family as well.
My car initially had an "incorrect" all chrome rear view mirror, (pre-68 or so; someone may chime in with the chassis VIN when the switch was made) which I had replated, restored with new glass AND new mirror, and sold on eBay years ago. As mine is a 1969, the later style with the matte chrome neck and plastic body is the correct one. I actually had the correct one in a box; my guess is my uncle found a chrome one at a "pick and pull" junkyard on Long Island back in the 70s and like it, so he swapped it, saving the old one.
Anyway, I did the same thing to the newer style, changing the glass and mirror. I don't remember this being any issue but I could not tell you how I did it. I do know that I took it apart (easily); had bought a pre-cut mirror from Miller's years ago, had a local glass shop cut the front glass, and snapped it all back together. The fact that I did this without present recollection means it was a pretty simple task. It's been so long I think it's due again...