Lift Kit for my Silverado

technically, 4" more ground clearance could be achieved with 2" of lift and 2" taller tires

or 1" lift and 3" taller tires

or as @barrrf said, 4" taller tires and no lift

edit: I also forgot 4" of lift and stock tires

or 3" of lift and 1" taller tires
 
technically, 4" more ground clearance could be achieved with 2" of lift and 2" taller tires

or 1" lift and 3" taller tires

or as @barrrf said, 4" taller tires and no lift

edit: I also forgot 4" of lift and stock tires

or 3" of lift and 1" taller tires

2" taller tires only gains you 1" of lift. So I was wrong. Under the rear diff ground clearance doesnt change no matter how much lift you put on.

Right?
 
right. only the tires/wheels would change difference under the rear diff unless you swapped out rear ends, but wont gain you much.