Update. I reached our destination with a fully loaded bed, clothes, food etc. I averaged 21.8 and that was doing 70 with the AC off and on. I'm hoping to do better on the return, but at almost 22 mpg for a truck this size I'm happy with the results.
Very good, especially with it loaded. If you slow down your mileage should get even better. My first pickup was a full size Ford. First trip with it driving at 70mph mileage was 13mpg. Slowed down to 62 mph and fuel mileage increased to 16.2mpg. That was back in the days when gas was cheap, less than a dollar.