I know they say "2 in lift" but they look like the shackles I have which are about 2" longer than stock (slightly longer than that but not a lot). They actually give you a inch of resulting lift NOT 2 inches. Find out what length they are, then measure your stock ones. You'll get 1/2 the difference in length.
The reason is you're only pivoting your spring down on one side and your axle is 1/2 way between the fixed point and the shackle. This means the axle only moves 1/2 the distance the shackle end of the spring moved.
But, maybe they're longer than mine. Keep in mind that with a 4x4 and it's shorter rear driveshaft you MAY require pinion angle adjustment shims. Otherwise sometimes you end up with drivetrain vibration from the angle mismatch between the transfer case (or tranny in my case) and the pinion. 2WD are slightly more forgiving because of the longer driveshaft.
Also, beware with a 4WD doing too much cranking -- you have CV's up there that don't like operating at higher angles so much. This means you'll probably wear them out a bit faster -- or real fast if you crank all the way perhaps. Some guys are doing this and don't have problems (yet) so perhaps I'm being "alarmist" -- but it's worth mentioning for the sake of discussion.