First, the right way to do this is to start with the vehicle tire placard. It should be on the drivers door frame. The placard will list the original tire size and the proper pressure for that size.
The second part is: The placard assumes you are towing within the limitations of the truck - so you need to know what Ford said about towing. If you are towing within the limitations, then the placard pressure is applicable (unless there is some additional advice in the owners manual.)
DO NOT use the tire pressure charts by themselves. Those are NOT recommendations. They are minimums.
DO NOT use the maximum listed on the sidewall (unless that is what the placard says to use.) The tire manufacturer has no idea what the load is going to be on the tire, so the maximum pressure on the sidewall is just that - a maximum, not a recommendation.
In all likelihood, your truck will call for a pressure less than the maximum on the front. Please be aware that Ford tested this truck at those pressures and unless you are willing to conduct your own tests, I think it would be wise to follow their specification.
