The factory truck hitches seem to be on the edge or under for limits. I replaced my factory truck hitch with a Curt XD because of this since my empty trailer tongue weight was just under the limit by 12 lb. at 1088 lb. Here's my specs old hitch and new.
Factory hitch:
Max trailer weight / tongue weight W/O WD hitch - 5,000 lb / 600 lb.
Max trailer weight / tongue weight W/ WD hitch - 10,500 lb / 1100 lb.
New Curt XD hitch:
Max trailer weight / tongue weight W/O WD hitch - 16,000 lb / 2400 lb.
Max trailer weight / tongue weight W/ WD hitch - 17,000 lb / 2400 lb.
I also have added Hellwig 2500 lb. helper springs to my truck.