I have made drivers side key locks for the 47-51 doors and posted a step by step on the Classic Parts site. The 52-55 1st can just use two passenger side units. If the 46 under the handle lock just raises a blocking tab in front latch release pawl then one could be made for a left side also. Since I am closing in on 80 I remember the REAL reason for the passenger side only locks. Many of the streets/roads in small towns were not all weather untill the fifties or later and the one side only practice had been continued from the thirties when nearly all roads were dirt. When they were mud you could slide out onto the sidewalk, be it boards or concrete, and lock up rather than having to slog all the way around the truck in the mud.
