Teen48,
Welcome aboard!
The bed on my '38 1-1/2 ton appears to have been built by the farmer that owned it. It has a pair of 4x6 sleepers that lie on top of the frame rails. It then has 4x4 cross pieces on top of those, and finally a 2" tongue and groove deck on top of that. All of the material appears to be fir.
There is a band of 2" x 1/4" steel lagged screwed around the perimeter of the deck that reinforces the stake pockets and protects the edge of the deck.
I remember when my uncle bought a new International truck in the mid 50's. It came as a cab and chassis and then he and my Dad spent a week or so building the bed and racks for it.
