I've towed a 7' x 12' trailer with 2 quads and about 600 pounds of wood on it before. Don't have any pics of doing it though.
Let me tell you, that was a nightmare to pull on the freeway with stock 4.10 gears and 35's with my automatic 3.8. Any slower than 59 and it would downshift, any faster than 61 and it would downshift, the only way to keep it at 59-61 in overdrive was to drive behind the semis. Ideally I would have kept it out of overdrive, but it would absolutely kill my mileage (down to about 10 mpg as opposed to the 18 (I know, I was amazed too)) that I managed to get that day.