You might think so, but suspension lifts, and AALs in particular, don't give exactly the amount of lift they are marketed as giving.
A '4 inch lift' might give anywhere from 3-5 inches of lift depending on what it's installed on. A lighter weight vehicle will get more lift than a heavier one.
A 2 in. AAL might lift the rear of an unloaded 2 door Explorer about 2 inches with brand new factory springs. With worn out springs, on a 4 door, with cargo in the back, you might get only an inch of lift or less. Just like regular springs, Add-a-leafs wear out too, and so it will give even less leaf once it breaks in and as it wears down. Sometimes AALs just restore the factory ride height to the original spring.
AAL's are generally considered a budget option, and are really better for towing, restoring height and firmness to used springs. They aren't the best thing to use for a lift or off-road, since the firmness they add hinders flex rather than helps it, and for off-road, you want softer springs, not firmer ones.
If you want a 4" lift, you may have to get something like 2.5" Old Man Emu lift springs.
Something else you can do though, which is WAY cheaper, is a SOA (Spring over axle) in the rear. Relocate or add leaf spring mounts to the TOP of the rear axle, use the stock springs, and you get 5.5-6" of lift. This also lets you use the stock length rear shocks if you locate the bottom shock mount in the same location below the leaf springs, but above the axle.
Then use the 4" lift springs in front along with the F-150 spacers (and a set of either a 4 or 5.5" drop brackets) and you get a 5-6" lift. Then you can go straight to running 35's instead of just 33's.
Of course, you can just get the 5.5" lift for the front intead of using the 4" springs and spacers.
This usually works out since you have to re-gear anyway, but you can spend all the money you saved buying bigger tires instead of a whole new rear suspension.
