2006 ram 2500 mega 4x4 cummins 5 ft bed. The reason I ask is the previous owner added leaf springs in the rear end. There is zero dip in her rear end and it rides unbelievably comfortable.
Your "tow limit" will almost ALWAYS be limited to the remaining payload after you load up people, hitch, firewood etc. If you are at gvwr before adding a trailer, in reality, you have NO ability to safely tow a trailer. Now if you have 1000 lbs, you have 10K lbs of trailer with 10% hitchweight, or 4000 lbs with 25% hw.
TO answer your question, who really knows, as it can vary!