When you remove the screw that holds the clamps around the top and bottom of the mirror, as well holding the clamp to the end of the ball on the stalk that is screwed in to your cowl, the clips can be removed from the mirror assembly that surrounds the glass and you will see that it is a frame that can be gently spread apart. It is much easier than you think. Here is the link to WLLW, which is an automotive mirror supply store that sells off of Amazon. I was quite pleased with the quality of their wares as well as their service (and I bought more than one mirror from them
). You might find that you need to replace the backing plate behind the original mirror with something a little thinner (since the new glass is slightly curved). A piece of slightly thicker, but not too thick, plastic works like a charm (I used a piece of plastic separator that I found in one of the kids school notebooks from decades ago -- just trimmed it with scissors). Then paint the inside of the plastic with a flat black paint to absorb light passing through the mirror and the outside, which would face the the front of the car, with a wrinkle finish black paint so it kind of looks like it did 50 years ago, dust the frame with a flat black, and you're done.
https://www.amazon.com/dp/B07H7ZFX5M...t_details&th=1