Although we are in the UK, my husband has a F150 Harley Davidson pickup but he wont let me use that for towing.....LOL...its his toy.
Check the specs for your particular truck, however... when I was looking at F-150s a while back the Harley Davidson model has a MUCH lower towing capacity then the other models. I don't know why, but I remember there was a big difference in towing capacity. If your husband ever reconsiders, check the specs for your specific model first.
As to the original post...
I pulled a 3H trailer (holding only one horse) through PA awhile back in an F-150 (V8 gas engine, towing package). Truck was rated as just under 10k towing and I was pulling about 5500-6000# (trailer, horse, tack, gear, etc.)
Some of the hills were not that easy. The truck did the job, but I would consider that the bare minimum in hilly country.
ALWAYS check the specs for your particular model/configuration. Engine size, tow package options, gear ratio and other factors all play a role in determining what your vehicle can tow. Not all "F-150s" (or any model) are created equal.
Also remember that even if your truck is rated to carry "8500#" it may not be safe to just hook that much up. Most vehicles have TWO ratings (talking bumper pull here). The lower rating is for a standard hitch. The higher rating is when using a weight distributing hitch.
Most car dealers have no clue about this stuff. Fortunately, most car manufacturers have pretty good detail on their websites (if you look hard enough).