My above comments were in regards to the fenders. (I didn't notice the comment about bed sides.) The fenders could be relatively easily adapted to a 1946 bed, and if done properly no one could tell the difference.
The beds have lots of differences, including a scrip tailgate and a different tailgate chain system. I have not studied the bed differences in depth. Anything can be made to fit but it will look like a frankentruck. It all depends on what you are trying to accomplish.
