The 4-inch lift allowed us to mount a set of 35x12.5-17 Pro Comp Xterrains (actual height 34 inches) on a set of 17x9 Extreme alloys. Though we ran 5 inches of backspacing--the directions say 6 inches is the maximum--we did notice a slight amount of rubbing on the back of the front fender flare on hard turns over ruts at speed, but it was nothing a razor knife couldn't fix.
As would be expected, the Rancho-lifted Ford was taller. The front of the truck was actually raised 5 inches and the rear 4, but the truck also sits more level now than before. With the tailgate open, you now need to lift hay bales or heavy coolers up to 38 3/8 inches (from 34 3/8 at stock), and getting in now means stepping up 28 1/4 inches from the previous 24.
Under the big Ford the front skidplate went from 9 1/4 inches to 11, and the center crossmember went from 10 5/8 inches to 15 3/4, though the mounts for the subframe braces hang down with only 13 1/8 inches of clearance.
Nevertheless, the belly-dragging stock rig was stopped quickly on the rough stuff where the Rancho truck didn't even scrape.
Even on the beer-can-deep ruts the Rancho Ford could roll through with little problem, thanks to the taller tires and better clearance, where the stock rig was constantly looking for creative lines for its smaller tires. The Rancho kit gains lift by using longer struts in the front and lift blocks in the rear. In addition, since both suspensions were running the same springs, the flexibility didn't change from stock, and the bigger tire had plenty of room to stuff into the rear wheelwells.
In the high-speed runs, the only complaint we had with the Rancho truck was that the bigger tires needed lower axle gears. The stock truck seemed to get up and go a little more quickly, but we were always on the edge of bottoming it out. The Rancho truck was great with the different settings the RS 9000s allowed, and we had no worries pitching it out in the dirt. The same held true on the road where we would have liked some lower gears to turn the big Pro Comps, and a speedometer adjustment would be needed since ours was reading about 5 mph slower than our actual speed.