To help prevent metal to metal contact when 1/2 and 3/4 tons are overloaded or have weak shock absorbers, truck manufacturers used a rubber devise. This cushion prevents the axle from making direct contact with the frame rails.
On the rear of the 1947-1953 GM pickups, it attaches directly to the underside of the hump in the frame. It is not meant to be removed during the life of the truck.
In 1954 a change in the overload bumper location was necessary. This was the first year for a redesigned step bed which was three inches deeper. To keep the top edge of this new bed the same as earlier years, the hump in the frame was lowered. It was necessary to place a bracket on the side of the frame rail and add this bumper. The attached photo shows this repositioning of the overload bumper.