All light-duty turck driver side doors have a weld plate with three threaded holes, to receive the sport-style mirror. Sometimes they are welded up or filled with body filler, but they are still visible from the inside of the door shell with the innder door panel removed. Additionally, the passenger side door shells have a reinforcing plate in the mirror area, with three holes drilled in it, that is also visible from the inside of the door shell with the inner door panel removed. These three holes are not threaded, nor do they have a weld nut, but they are in the proper location, as determined by the factory reinforcing plate on the inside of the door skin.
If you locate them, in a location other than where these holes are, you run the risk of hitting half the hole and wallowing out the outer sheetmetal skin, when the bit tries to run into the factory holes.
