You will get tons of debate on this. Some people swear by the ZUK, others think sticking a spring between a rubber bump stop and it's frame contact isn't the slickest idea... to each their own I suppose.
New OME spring packs? They usually wind up being quite a bit of overkill if you aren't looking to lift the front. You will be left with a healthy rake.
What is your reasoning for AAL being the best for "nothing"? Strengthening the existing leaf pack with a good AAL, like a long leaf from rancho or taking a leaf or two from another leaf pack is the best option IMO, especially for a daily driver/street driver. AAL can get a bad rep because some guys throw leaves in the truck that are essentially cheap, thick and short bars that force a spring pack back into position. That is not what I am referring to here.
There have been a few times where 4runner owners have purchased all new OEM (not old man emu) leaf packs and found the truck to be no higher in the rear, not restored at all. These things came right out of the factory hanging pretty low in the rear. Adding good quality soft add a leafs is the most professional way to go IMO, over a ZUK. Old Man Emu makes great spring packs, but most find they need to lift the front then, and that starts a new can of worms.
Remember, the rear fenders are cut two inches lower on the body, so if you baseline measure (unloaded) say, 14" from top of your wheel to the bottom of your fender in the front, the rear should be at 12" (for example).
Once you measure with the truck on a nice level surface you can get a baseline and see how your rear springs are sitting or handling the load. Even if you find they are not sagging and are basically stock, and you decide it still doesn't look right, adding to the leaf pack gives you the power to lift as little as 1.5" at a time. If you throw medium duty OME spring packs in the rear you will get a significant boost over stock, which may look strange to some.
