You could do it on either. The 2wd and 4wd have lots of travel and once the chassis hits you will see the shock shaft is not bottomed out and that extra is where the trouble can be. The truck honestly don't need that extra and most of the time what happens is the shock gets pushed up farther than needed and either hits the bladder and can cause a tear or worst case as many has had happend pops the shock top off. Once I put the extra tubing on the outside of my shocks I never popped off another stock shock top.