Easiest way is to add a hitch receiver to the front of the truck and use something like Yakima's "Drydock" at the front and a standard cross bar on the cab of the truck.
More expensive but more versatile are racks that mount on the rear of RV's and trailers from RVracks.com that hold up to 4 kayaks mounted vertically (11' or shorter are best) and can hold 2 kayaks along with 2 bicycles.
Inflatable kayaks are at best a last resort. Heavy to move around, time consuming to unpack and repack, and a big problem in terms of inspections for quagga and zebra muscles as they are very difficult to get 100% dry before packing them.