I've got a RCLB 4WD with the 5.7V8. Got 17-ish mpg on the drive back from NC and getting on it occasional around town dropped it to 14-ish mpg. I have not seen another RCLB truck, they are all short beds.
I read that Toyota dialed back production on the worktruck and are increasing production on the crew cab to meet demand. Whoever in Toyota thought they could sticker a pretty stripped worktruck for $29K was smoking some good stuff.