While the truck is rated to pull 8000#, I pulled a 5000# trailer with the same truck. it worked pretty hard, but I guess it did OK. I would have proably gone 6000#, but that would have been tops for me and still have a margin. Watch tongue weight and payload. Those are going to be your weak links, and remember, air bags will not increase the carrying capacity, they just make it level.

 

I tow a 2009 Weekend Warrior Carbonlite...loaded it weighs between 5500 -5900 lbs..I have had it in Nevada,Arizona,New Mexico and Texas..has been just fine with the 4.6..I have over 3k miles pulling this setup..If I were over the 6k range I would want to jump up to the 5.7 motor

 

This is not a direct comparison but it should help. I have an 06 and pull a bumper hitch horse trailer that clocks in at right around 6000 loaded with three horses. I don't pull every day and opted for Timbrens instead of air bags. Gas mileage can drop to around 9 if you push it ,but it works out fine in most situations. I would not want to take it to the mountains if I had more than one horse in the trailer. Your truck should be able to haul around some serious "toys" in my opinion. Good luck.