I stumbled across an interesting article from Ford Vehicle Capsule Reviews:
Gas mileage was an important consideration in the 4WD Standard Pickup Trucks for 1999. Heavier than last year, Ford's is a 4WD Standard Pickup Trucks in the fullest sense. But we think it will be different for the 1999 Ford Super Duty F-250, which seats

Found at: Ford Vehicle Capsule Reviews