I've towed my bronco loaded on a steel flatbed 18 ft trailer plus camping equipment, spare parts, tools, and an extra set of tires behind my '97 expedition and it works fine. Some things to watch out for:
- when it's all loaded up the rear sits a little low so I try and avoid night driving as the headlight angle isn't optimal (you can add lift bags to help offset the problem)
- I added a tranny cooler and a brake controller (must use trailer brakes with a heavy load like an EB)
- I've got the 5.4 liter engine and use the overdrive when I tow as long as it doesn't have to hunt for more gear. The manual advises to turn the OD off, but the high engine revs at 65 mph and the 8-9 MPG sucks so I use the overdrive and get 10-11 MPG at 65 mph. Some folks have advised it will ruin the tranny but I've been towing for 15 years and have about 170k on the truck (same tranny), with at least 10k-15k of those 170k towing the EB.
- No you probably won't make it over Vail Pass fully loaded, but small hills and flat roads are just fine.
It will never compare to a diesel when it comes to pulling a load, but it also won't cost anywhere what a diesel costs either.
Good luck