I have the same truck and a 4000lb 9.6 Bigfoot (loaded up ready for the road), I ran a stock suspension for several years and it worked fine. I takes two days after loading the camper for the top overloads to touch, so I don't think extra leaf springs are required. I have installed rancho 9000's shocks which has reduced some sway but really no big improvement over the stock shocks with 140000 miles on them. I think the stock sway bar is a little on the small side and wish I had invested in a heavier one instead of the rancho shocks. I run 60 psi in the rears and 65 in the steering tires.
Like jefe says get a good fuel lift pump on your truck.
It looks like you also have a 2wd, if you have any issues with some steering wander like I had, I was able to resolve this by installing a steering stabilizer, its a bar that connects the frame with the steering gearbox output shaft, the frame where the gearbox bolts up to the frame tends to beer can and can cause minor wander problems.
