I run the HD Timbrens on my 2500 with a Wolf Creek 850. I initially had just lower Stable Loads which worked great in helping with sway and some with rear end squat. I added the Timbrens to help with the added sag caused by the addition of my 16' trailer with ATV's, extra gas cans, firewood, coolers, etc. The Timbrens work great for me to help keep my truck level and no added sway. I don't know if I really needed the HD version of Timbrens, but I figured it couldn't be a bad thing so that is what I did.
I've had good experience with added leaf springs on previous trucks also but I wanted my current truck to fit in the garage and didn't have room for the added height springs made. Timbrens do not effect my unloaded ride or height.