I'm not sure what you are thinking of when you say "type" of shock. While some people will have strong brand preferences, most any good brand of shocks designed for your make & model of truck will do the job. Shocks don't increase tow capacity or anything like that. Some people like an adjustable shock like some models of Koni brand because it allows you some control over the stiffness of the ride. For most of us, though, it's just install them and forget them until they wear out and the ride and handling gets bad again.
You could get ones with an extra spring or air-assist to provide additional rear end lift if you thought was was helpful, but I would think a 4700 lb trailer would be well within your truck's tow capacity and nothing exceptional needed.