I finally got the Scamp hitched to the truck to see how things fit. I knew I'd need a relatively level, empty parking lot to get some measurements which was an illogical thought for Black Friday. The Baptist Church down the road had a reasonably level spot in their lot so that's where I went.
The truck settled about 2.5 inches with the 700 pound tongue load.
I was expecting 7 inches of bed rail clearance but ended up with 8.5 inches. I'm real pleased. When I started shopping I was working with a 6 inch minimum in my mind - really nice to have that extra 2.5 inches.
I set the hitch further back from the normal position for a fifth wheel hitch, but wasn't worried about that since the tongue load is less than the tongue load limit for a standard trailer with this truck. I've still got plenty of clearance between the tongue and the closed tailgate.
The mod of the 15K Reese hitch was super easy. Just pulled the pin that held the original fifth wheel and replaced it with a piece of 3/8" steel bolted to the structure using existing holes.
By mounting the hitch further back, we have tailgate clearance. Should have 1/2 inch or so even when the truck is at 45 degrees to the trailer.
I'm super please with how it's all fitting together. I drove it a few miles and like the way the truck pulls, the transmission shifts, and the temps I was seeing. The next big test will be a quick trip to Yuma. Time to go visit a Mexican dentist.