We used a folding bed rail, sort of like this 30-second find - ClickyOurs nearly touched the ceiling, and left just enough of an opening at the foot end to crawl out.Have fun.
I'm running DH-01 Hankook 265's on a stock height Ford Superduty. No clearance issues unless loaded heavy and turned full stop across off-camber surface. Turning radius on the leaf sprung Superduties sucks, so I'm always looking for a football fiel...