I'd argue that the top +2.25" position would give the most "dead-level" look, however, every truck is different and it also depends on the condition of your suspension as to the final geometry and ride height of your front end. You may want to play it safe and start it out at the middle +1.5" ride height and see how it sits. Still, the tallest position is most likely to give your F150 a fully leveled look.