The Stovebolt Site Forums The Shop Area Making a Stovebolt Bed Frame Rails and Hole Purpose

I am trying to make a hitch for the AD Pickup and need to know the exact purpose of all of the holes on the side and top of the very back 7" of frame rail. I already know the two on each side for the bumper bolts and the center one for rivet relief, but the other ones I am not sure. Is there a diagram somewhere for 1950? Thanks!