If you install the bed on a model A frame, you need the metal piece to clear the rear frame crossmember, otherwise the wood would hit the crossmember. This is why Ford put the metal part in the bed. BTW, Ford used a piece of webbing riveted to the underside of the metal plate to prevent rubbing and squeaking. If you don't use the metal piece and raise the whole bed up a little to clear the crossmember, the rear fenders and splash aprons wont fit right.
Rusty Nelson
