Answer:
10,000 lbs... BUT!!!! add larger rotors, larger brakes, and if you are running a 97 then you need to change the injectors... California passed a law regulating the emmisions. to fix the problem ford changed the injectors, lowering the horsepower.
after you change all of this you can safely pull up to12,000 lbs. stopping of course is another issue. i sugest an engine brake accompinied by trailer brakes