I question the nothing in the truck bed and no family when researching a bunk house, bit I'll run with all the numbers work out.
Your truck with 3.5L EB and 3.73 should be great for power. I would recommend the EQ 1000 or 1200 pound bars. At 720 pounds dry, should be a little under 1000 pounds loaded. Ford recommend you only need to restore 50% of unloaded front axle weight for your year truck. I would target closer to 100% based on rear axle load and rating. Many RV ownners with late model F-150s that have taken their setups to scales show rear axle rating (around 4050 pounds) exceeded under all other ratings @ 50% front axle weight restored.
Timbrens, air bags, and add a leaf do not transfer any weight from the rear axle to the front. 1000 pounds of TW dropping on a ball will take off about 400 pounds from the front/steer axle and add about 1400 pounds to the rear axle. While these rear suspension aids can change 5" of sag to none, they do not change that 1400 pounds. A WDH can take 600 pounds from that 1400 off the rear axle and restore the 400 to the front axle.
