Yeah, that's why I had to order a hitch, the ones in stock at my local auto parts store were rated for 5,000lbs without weight distribution or 6,000lbs with weight distribution.
The hitch I ordered is a Reese good for 7,500/12,000lbs, and was only $10 more. This is way more than I would ever pull with my Bronco so I will be in good shape when it arrives.