I just went through the same thing. After much consideration I purchased a set of rear springs from a performance shop in Walnut Creek California. The springs came in 3 flavors, regular, heavy duty and cargo. Of course I went with the cargo! And I love them. It lifted the rear right up and made the whole truck ride level. Plus, when I put my heavy paint gear in back or tow a trailer, it handles it no problem.
I usually work on my own cars but in this case I had a local shop install them for me. They only charged me $150. The whole operation cost me about $275. It was well worth it. Good luck!