You need to look at the GVWR stamped on the door frame of your truck and keep the weight below that value.Most people don't like to talk about the GVWR of a truck because in most cases RV hauling vehicles are overloaded. Calculate the weight of your truck with a full tank of fuel ,hitch and passengers.Add the pin weight of your big horn that may be 3200 lbs max.ie .. total truck weight 7500 lbs + 3200lbs (pin)= 10700 lbs. The GVWR stamped on your door sill should be greater than this value to be legal and safe.