Hey, Dr. V, not to hijack this thread or anything, but on my drivers side mirror I didn't have any screws at all except the one holding the base to the mirror shell, and on the passenger side, the mirror head itself was pressed on, rather than screwed on. All I had to do to get the actual mirror head out was to pry it up and out from the shell. I've seen other posts showing the goofy screw locations for some 1970 mirrors. Almost seems like there were 2 different styles of how mirror heads were attached to the actual shell.