gotcha
things to look out for; the spring over lifts are notorious for axlewrap; it happens on hills, in holes, etc. what happens is the rear wheels 'hop' and don't stay glued to the ground.....
the spring over also gives you about 5 - 6 inches of lift, and will kill driveline angles. you will need a slip yoke on the rear; or at minimum a tcase drop. i run 4" springs and still need the drop........
in short, just the spring over is not a cheap lift; it will hit you in many other places!
the reason the 4" springs are so common is because it works really well
if you want something 'tall' do a 4" spring under and do a 3" body lift.
maybe another question to address is what size tire do you want to run? stock yj axles blow, and anything over 33s will be really sluggish and potential to break stuff is present. plus, a 6" lift on 33s will make ur tires look small.
anyways, just some ideas