What is the towing capacity of a 1992 Chevrolet C1500 pickup truck with a 5.7 liter engine?
Do not go by the GVWR on your door jam. This only tells you the Vehicles Gross. If you can't find the rating. The best way is to take the GCWR (gross combined weight rating) and subtract the vehicles weight from that number and that will provide you with your trailer towing capacity.
Side note: Your tow rating from the manufacturer is related to the vehicles braking capacity. It doesn't matter if you can tow it, it matters if you can stop it.