I had about an 1-3/4" List to the left side with the TC on the truck. I installed new heavier 4400# rear leaf springs and the list is much less. I plan to install heavier front springs and that should get the rest of the left list or lean out of the truck. My guess is at some point in the trucks life it hit a hard bump under load and took some arc out of the front left spring which is a visible amount compared to the right. The truck carries the TC much nicer now. The unloaded ride doesn't bother me at all.
Here's a video of the installation. There are many other options available to address your one sided lean.
Installing 4400 pound rear leaf springs. 
