Go 861's if you've got a lot of weight in the back, carry a lot of gear, or like a good raked stance. I've got 861's and my rig is about as heavy as they come at this point. It sits good unloaded, and even with a FULL load I still sit with a slight rake. In my opinion 861s are the only spring up to the task of carrying weight. My only suggestion is to wrap the top progressive coils in "spiral cable wrap". I had a terrible noise from mine around 40mph where the coils would vibrate and resonate off each other. I put some of this on yesterday and the noise went away! It would have been so much easier to do off the truck though.