The owners guide says, "Your Ranger pickup is not recommended for slide in camper bodies." Your 98 S/C 4x4 would have a curb weight of around 3650 pounds. Add a driver and passenger at 350 pounds and you are at 4,000 pounds. Your GVW would be probably 5020 pounds unless you have payload package 2. Your rear axle GAWR would probably be 2700 pounds. The rear curb weight is around 800 pounds per side or 1600 total on the rear axle. Add the 1400 pound camper dry weight and the rear tires would see 1500 pounds per side. Then add in some cargo, 25 gallons of water and tools, etc. Pretty soon you are 5-600 pounds over the rear axle rating and most of the weight is higher in the pickup box then a load of gravel, sand or dirt. Your stability during high winds and sudden lane changes would not be good. Start to see why Ford does not recommend slide in campers?
I don't want to sound like gloom and doom, but I want you to be safe if I am out there somewhere that you are driving.