The link that Sputnik posted shows the frame mounted stabilizer. THIS is the best investment to cure wander.If your box is decent, put one of these on your truck. You'll wonder why the factory didn't do this...it'll be a totally different ride!!
We started using these at the dealership a few years back, and you wouldn't believe the customers that came back in and said their truck never steered that good from day one. For a couple hundred bucks, I think you cannot NOT afford to try this. Takes about 1 hour to do.