The snow plow package makes the front of the truck able to carry extra weight without sagging much. It is hard to make the front of the truck drop when loading a fiver in the bed. I have the snow plow and camper package on a F350. The front is pretty stiff. The easiest solution to make the truck level would be to install the 4" blocks on the rear of the truck. Then the nose of the camper would be real high. I would lower the pin box on the trailer and if it tows fine, leave it alone.
By the way, Nice looking rig.