With a 4th gen, you could probably do it. They have the crossmember that goes under the bumper and the ball bolts to that. I would not try it on any other generation Ram...too heavy.
About the only thing you can tow on your bumper is a Lawn Mower. The 4th gens have a crossmember that goes from frame rail to frame rail under the bumper and is welded at each end where it meets the frame. Your bumper is simply bolted onto the end of the frame rails.
To be honest, I am not even sure how much weight mine can carry on the bumper...but 3200lbs of car on a trailer would be pushing it I think with mine. Let alone an older gen.