Im not 100% on this, but Im pretty sure the bumper is rated to pull like 3000lbs - I know Explorers were 3500lbs pulling on the bumper... Check the max gvw, should be on a sticker inside the door. With 2 average sized passengers, your B2 weighs around 4000lbs, so subtract that from your GVW, and thats how much you can pull in an ideal situation (good hitch, your truck isn't loaded with stuff, ect.)
Also, I wouldn't want to be putting more than about 2500lbs behind the automatic tranny, especially if you have to go up/down lots of hills.