For towing the first thing I check is the gearing for the truck. For a gas engine I would want 4.10 gears and with a diesel engine the 3.73 gears if I was going to be towing a heavy load all around the country and over the mountains. I would also be buying a GM or Cummins diesel to get the better engine braking performance but you are set on a Ford.
60,000 miles is not a lot but an area of concern is the front end. Few owners even know to lube the front end of their heavy duty trucks and this increases wear on very important components. Not a big expense to repair but if it needs new tie-rods I would want to negotiate the price based on this information.
Most likely you will be replacing the shocks and brakes but rotor replacement can be more expensive and I would want this checked out as well. While the truck is in the air the mechanic and look for any signs of body repair that might have been done to the truck.
There are probably service bulletins and other information for this truck and model year so you know what the weak points are and what may need to be repaired in the future.
If I was looking for a used truck I would avoid one that had been lifted or had oversize tires put on it or had been used for towing. No way to know how badly the parts have been abused so best to avoid the truck altogether.