While our 5th was on order, I drove over to the RV dealer, and backed under a similar unit that was leveled and measured kingpin plate to bed, bedrails to 5th, etc. then you have to add a swag 1-2" for truck squat, and if the gap between bedrails, and 5th isn't somewhere around 6" then add that to the difference.
Or just throw your hitch into the truck as best guess, and head over to your selling RV dealer, and see if they will let you back under another, and do a hookup.
either way, you wont be waiting until D-day (deliver day) to find out if you are right on or way off....
Dave
