I went back through my literature collection and lights are conspicously absent in the factory literature, both brochures and ads. However this is a shot from a dealer lot here in Utah, notice the lights out on the cabs on the outside corners.
https://www.flickr.com/photos/advance-design_parts_co/13918867461/in/album-72157631872034068/
This is a 1949 2-ton I parted out a few years back (Utah truck) and the lights are in the same location.
https://www.flickr.com/photos/advance-design_parts_co/8130559770/in/album-72157631870734114/
Here is another Utah farm truck with a similar arrangement so I would conclude our local laws back then mandated the corner placements.
https://www.flickr.com/photos/advance-design_parts_co/23184806264/in/album-72157631870734114/