Airbags will help you level the load, won't help you any more with pay load, which is going to factor in on cargo carrying capacity of your truck.
I would look for a light 5er...but first, I'd load my truck up like I was heading out to camp...go weigh your truck, add 200# for a 5er hitch...when you weigh your truck and add the 200#, look at what your trucks GVWR (sticker on the drivers side door jamb and subtract what you weighed from the trucks GVWR, (ex....weight of your truck is 5,000#, add 200 more for 5er hitch...equals 5200#...if GVWR is 6800#, it means you have 1600# of payload left you can put in the bed of your truck.
do yourself a favor EARLY in this research. DO NOT use "empty or dry" weights, they're a joke, no one tows the 5er "empty" or "dry"...Take the 5er's GVW and take 20% of that and it'll give you a "ballpark" of how much pinweight you'll put in the bed of your truck...(ex. If 5er has a GVW of 9,000#, the pin weight could go as high as 1800#.. THIS IS key.
I've towed a 27' 5er with no slides, thinking my 5.3 chevy with Tow package could do it...it was terrible...that's my experience with a 1999 Chevy 1500...towing in the mountains was miserable and I went to a 3/4 ton truck.
I would look really hard for a light enough weight 5er to where it doesn't abuse or wear out your truck prematurely due to weight of the 5er.
hope this helped some.
ON EDIT: I have no idea what the GVWR rating is on your truck some Ford owners will be able to help more, but believe the Eco boost is supposed to be a pretty good truck, but again, I watched the weight and go by what those familiar with this truck will recommend you do.
Be nice to know what the GVW of the 5er you're looking at is....very important tidbit of information to be sure.