I'm doubtful at this point that its a factory install, the crossmember that supports the watson is very home-brew looking and the shifter install and trimming of the access panel that covers it is definitely an afterthought, I will post more detailed pics now that I have the bed off.

The story I got when I bought the truck is that it had spent its life in Ontario Oregon in Ore-Ida potato country hauling beets and spuds. It had a sister COE the same color. In the area was an outfitter that added tag axles sucs as the one mine had and brownies to make these rigs capable of the heavy loading. The old boy I got my truck from thought this truck had probably been upgraded locally long-ago