Here is a link to a site that sells something similar, but they are expensive.
Also, my brother in law had a 6 wheeler that was 54 inches wide. He had a pickup rack and a full side to side tool box in the back. He used two short ramps laying against the tool box and two long ramps from the pickup to the ground to get up in the pickup. The short ramps were mechanics car lift ramps laying on an angle against and on top of the corner of the tool box, they are about 2 1/2 feet long. He used the winch on the six wheeler hooked to the front and top of the pickup rack to load the six wheeler onto the pickup. The front tires rested on top of the tool box, the rest of the front of the machine was above the roof of the pickup. I can't get a picture. He died. It worked real good and he was still able to load his hunting gear in the back of the pickup. Any deer or elk he got would have to ride in the passenger seat of the six-wheeler or stuffed between the side of the pickup bed and the vehicle.
I have seen a guy that had a system built that would lower down to the bed and ground at an angle. You would then pull up on it. Then he used a winch in the bed to pull the rack back into place. He was able to haul 2 fourwheelers in the back of a truck this way. Now one thing you need to think about is the extra weight above. You have a big enough truck it shouldn't hurt but keep it in mind.