I always go with what the Tire Manufacturer's recommends NOT the Car Maker, usually 2 to 4 pounds under Maximum. Yes, hard ride, but tire life like 90,000 miles plus on Ford and Dodge One Tons.
I always run 30 to 31 psi on mine even though recomended is 32 psi all the way around...rides the best and still gets good tire wear and at the track around 20psi unless im running drag radials then i run around 14psi