f150 is fine for flat areas. You're screwed if you have hills or you are going to park in the fields with the clay in these parts.
AND GET THOSE WEIGHT DISTRIBUTION BARS. EEEEKKKK!
I would keep the trailering to an absolute minimum as you will have tranny problems later on. And stick with flat areas, no hills. Be slower and further away from other cars as you won't have the stopping power.

Average, for horses with some experience at this level