From my expierience, the weakest link of the setup is your truck's frame and the amount of load bearing surface where the hitch bolts to it. After about 50,000 miles of towing a 5,000# trailer with a D150, while snapping the torsion bar brackets up one day, I heard a peculiar sound. When I crawled under the truck to investigate I found the frame ripping apart like a piece of paper. Lucky for me this happened in my driveway!! The frames on our trucks are a lot thicker and stronger than that D150, but it is something I will never, ever forget.