My '39 3/4 ton has a mount on the left between the door and the rear fender. It's a simple affair, and probably was built by the local county shop that took delivery on the truck. I have owned the truck since about '61, and have driven it coast to coast and into Canada and Mexico, and have never noticed a vision problem with the mirror.
The mount is simply two flats of steel about 8"x8" with a spreader long enough to clear the bed with the tire. One flat is bolted to the side of the box, and the other has three bolts that fit the wheel pattern. It works well. This truck was, and will be, a daily driver, so practical rules.
Also, I seem to remember people wanting to load the left a bit heavier because the right side is more prone to running in the gravel, or off the edge of the pavement, and they tried to even wear on the tires. I doubt that is any longer an issue, though, so...whatever floats your boat.
