Because the axles are under the springs removing leafs in front will immediately lower the truck the thickness of the spring and possibly a small amount more.
In the rear the 'overloads' are not supporting anything until the truck is under significant load, so removing them is not going to change anything.
Lowering one of these trucks very far is probably going to require a more radical approach and it will no longer be a 2-ton truck when you are finished.
