I don't know if this will help, but on my '46 half ton project, overloads were installed and apparently used frequently. I've seen at least two others with these same overloads. As I understand it these were all aftermarket additions and are not shown in the accessory catalog.
I recall seeing replacements rubber bumpers, but don't recall where. They were outrageously expensive IMO. I decided to make these myself, given the truck was never going to be used to haul grain or other heavy loads again anyway.
An inner rubber slab from a skid steer tire was used. Regular tire rubber was tried, but it was much to stiff and wouldn't flex enough to fit into the bracket.
I can post photo links if anyone is interested.
