Or more importantly, how can I figure it out?

I just finished new disk brakes on all four wheels, new wiring including a trailer harness and already had a ball hitch. It has a 350 installed and a 400 tranny. Newere rear end although I can't tell you what.

I want to attach a trailer to pull ATV's etc but have no idea how I can determine what the load max is. I can put airbags on the springs to lift it, and I am confident I can stop, but it still ahs the original radiator and wonder just how much I can handle?

Also a naive question to show you how inexperienced I am, does dual tires on longer trailers lower the gross weight on the hitch? (ie make it easier to balance and pull?)

http://s615.photobucket.com/albums/tt231/RandyMohr/