Old Man Emu are great springs! I put them on all 4 corners of my F-250 Super Duty.
Depending on the kit you ordered, OME springs will lift the vehicle 50 - 55mm front/rear. The kit isn't designed to level your load. The kit may carry your load, but as mentioned, not a leveling component per se. The air bags are designed for load leveling. Take a hard look at BOSS Air Bags.
Also, I would encourage you to bite the bullet on load range E tires. Many folks put off the purchase to wear out the existing tires. While a load range D tire may suffice, the potential for a blow out is greatly increased. The Fleet likely weighs more than the designed load of the truck's bed. This will have a pronounced affect on LRD tires, especially on gravel roads and tracks due to fewer ply in the tire construction.
I would strongly encourage you to purchase LRE tires now. You can always Craiglist the existing tires and get some cash to help defray the cost of LRE tires.
Consider the purchase of load range E tires as inexpensive insurance!
I even replaced my factory spare with a LRE tire. You don't want to be 20 miles down a track with a blow out and a LRD spare tire to try to get out. A double blow could leave you stranded for days.
Yes, the dollars add up prepping the truck for the camper. But, best to do it right the first time.
Like the old FRAM commercial, "you can pay me now or PAY me later"!