I have a 66 stepside and I ordered a round original mirror from Chevy Duty for the passenger side. When I installed the one for the driver side thee were three dents indicating screw placement. I don't see anything like that on the passenger side. Any ideas.
We did the same thing on our 1965 lwb. We just made up a paper template from the drivers door and copied it over to the passenger door. The drivers door has threaded inserts but the passenger door doesn't so we just added large fender washers and nyloc-nuts on the inside.
I did the same exact thing, paper template, double check all the measurements once it's marked - but instead of nylok nuts I used the serrated flange nuts (with fender washers) like shown below. It's a tight spot up in the top of the door and they are easier to get started since they don't fall through the wrench as easily. http://www.smithfast.com/serratedhexflangenuts.html
When we took the door panel off of our '66 and looked where the mirror supposed to go, there was a bracket welded on the inner door with the same hole pattern as on the mirror base. Using the template as the other guys advised, you will be able to drill, (using a small bit first), right into the welded bracket. This worked for us, not sure if anyone else had that bracket in there.
Yeah it will be interesting to see if anyone had this bracket. It already has the holes as the mirror base only they are not threaded like the drivers side. Just need to drill through the door and into the bracket holes and you will be good.
I guess it can go either way, we have had the truck in our family since 1982, and knew the first owner before that. I dont know if he ever replaced the door or not, but we haven't. Still a pretty interesting issue.
More-on mirrors I put the big rectangular mirror that our host offers on both sides after removing the huge vertical mirrors the previous owner installed. Threaded back plate on driver's side and threadless back plate on passenger side. The flanged bolts our host sells as stock replacement are long enough to put lock washers and nyloc nuts on. (or whatever attachment scheme works for you) If you have 'Man-sized' forearms it is going to be a challenge getting the hardware on the bolts inside the door. I crazy glued the washer and nut together so it was one piece and managed to get it started with index and middle finger. Incidentally, the triangular rubber gasket that goes behind the mirror mounting plate makes a good template for hole registration if you measure driver's side for placement.
