With the Rancho 9k's on the rear you can set them soft for mt or adj to the load. Since the front load wont change more than a couple hundred #'s you can go with any good mediun duty shock.
The camper/ overloads do not affect the mt to moderately heavy ride as they only engage the ol spring saddles when the mains compress to that point under load.
Any shock will help the ride as long is it is not an OEM. They should be replaced PRE-deliver as part of the pre-delivery service, along with the tc/ valve body, clutch, stock injectors, exhaust, air box... ... ... ...