Not much. You're going to have two problems here.
1) Towing with a 4 banger is going to make for painfully slow acceleration.
2) Towing with the auto trans is a good way to destroy it. I'd get a nice huge trans cooler if you're going to do it.
If you had a stick (manual transmission), I'd say hitch it up and see what it'll do. You won't hurt a 2.5 trying to move too much weight with it, but you will probably get the finger from other drivers who don't like how you're slowing them down. But i'd be careful with the auto trans.
FWIW, I believe your truck is rated by Ford to tow 2000 lbs (this is the lightest tow rating for a Ranger).