Hoooowwwwdy!

Well here you go... I took the mirror to my local mopar mechanic and at first glance, he was baffled too! He said he had never seen a passanger side mirror that did not have a stud comming out of the bottom but instead, a screw hole that is "hidden" when the mirror is in it's normal position for driving.
His son was watching us and exclaimed, "we have one of those in back". He ran off while his dad had the look of disbelief. Sure enough, his son returned with the exact same mirror as mine, even the part number was the same! The two sister right hand mirrors were reunited! The one he had brought back had something rattling inside that turned out to be the original mounting screw. With a little manuvering, he got the screw to fall back in it's hole. I remembered that when I bought mine, it had the exact same screw. I thought that someone just rigged it with this since it was too small to fit in the factory hole in my door. My mechanic said that Chrysler sometimes used multiple sources for parts and this may have been a company they used for a while and then went to the stud type exclusively. So, this unit was probably used in the 60's and was screwed into the body sheet metal instead of having a mounting nut underneath. My first instinct was correct. I'll use a 1/4" coarse thread machine screw head with a tapered phillips head and a nut on the other side. \\:D/