So far, the only ladder racks I've heard about are ones that install in conjunction with tonneau covers or caps. I am not sure whether they are proprietary or whether they struck deals with various rack makers. I'm no expert on ladder racks, but most of them either install their own rail system or make use of the vehicle's built-in track system on trucks like Toyota, Nissan and Dodge from what I can see. Have you tried calling invis-a-rack and some of its competitors?Had anyone installed a ladder rack in the bed yet? This will be a necessity for me but I don't see any posts about it yet. The invis-a-rack is my favorite addition to my current truck but they haven't gotten back to me on whether or not they are making one for the RL.
You know what the truck world needs? It needs a common specification, short-profile truck rail add-on for adding accessories like racks, tonneaus, caps and the like. The major manufacturers and parts makers should have an industry group whose job it is to meet and figure this out. That's how we get things like Wi-Fi, Bluetooth and most recently Thunderbolt 3 in the computer world.