My car is a July 65 Dearborn also. Mine has the steel jamb switches. I've included a picture of one of my originals that I replaced because it was in such bad shape. I also have a picture of the hole. this old switch clips right in. I don't know if there are different metal jamb switches but here's measurements from mine.
The hole in the door jamb is an 11/16" hole and is 7/8" at the widest point of the cutouts.
The metal switch measurements are as follows;
Plastic is 11/16" diameter and just under 5/8" across the flat portion
The metal ring is just over 1" is diameter
Just make sure the metal clips are on the inside of the ring so it can compress when you push it in, When I was putting one of mine in one of the clips was outside and it took a little for me to figure out why I couldn't get it to pop in.
Dave