I just picked up my truck this afternoon after having the leaf spring TSB upgrade done. It has four leafs on each side like it is supposed to.
Regarding having un-equal sets of springs between the left and right sides, the spring rates need to be equal on both sides of the truck. What would happen if there was a driver and a passenger sitting in the cab plus several hundred pounds of cargo evenly distributed in the bed area the way cargo is supposed to be distributed? Having un-equal spring rates could cause loss of control. I am surprised the service department at the dealership thought having four leafs on one side and three on the other was normal.