mem,
Welcome to the Stovebolt. Tim speaks the truth. I bought a '54 naked cab that had the small hole directly above the headlight switch hole, which is on the left side of the steering column.
I think Tim is actually the person that pointed out that this was the location for the starter push button for a Hydra-Matic rig. If your cab really did have this transmission, the transmission cover on the floor will be different too. Instead of being almost flat with the floor, the cover will extend up the toe-board for 4" or so.
There are probably more clues, but Tim would be the expert on those...my find was just a fluke.
Stuart