I may have to change the name of this truck to "The Onion" every time I pull something off I tend to find an issue. Fortunately I've literally gone from the front to the back and there's not much left to discover.
I removed the roll pan and found that the rear bed sill had been cut to accommodate the license plate recess in the roll pan.

Looks like I'll be replacing this and when I start on the wood bed.