Another option or two for you to think about
Hey,
So I also had the same issues you are having with the rear adjustable suspension (RAS)... and its a pain to deal with. The chassis is different from the typical 4th gens as it has completely different mount, so there's no kits made for this. By adjusting the height sensors, you can increase the height. If you do this, put it to the max and never go more as you will do damage to the bags, also the ride will be much more stiff all the time possibly wearing out the bags much faster. Saying this, its tricky and you have to get both sensors in the exact same location. Better yet see if Toyota can get into your computer and change the "0 set point" for the sensor (I tried this and Toyota said "no way")
Another option I looked into was to install a custom fabricated spacer directly on the axle just below the lower mount. This will allow you to still use the adjustable controls. Essentialy to do this you would require cutting off the exsisting lower mount, putting in a fabricated spacer and putting the mount on the spacer and welding it all together. Spacer will need a half inch hole through the center for the Pin that sticks out of the bottom of the airbag and locks into the mount. Sounds simple enough but it would be a hell of a job, especially on the left side. Have a look under your 4runner and you will see what I mean. Keep in mind that the airbag rotates out 180 degrees from lower mount (no problem when removing it as you would cut off the lower mount and spin it off, but for installation you would need to do everything from above as you will damage the airbag if you weld the mount while lower pin is inside the mount) and you cant disconnect the xreas system as there is no charging or air bleed connections on it, its a factory install only (tricky to spin it 180 degrees). Also for this you will need to extend the arm on the height sensor as it will not reach the upper location.
In the end I just went to work with a grinder, and got everything out and started from scratch with a naked axle and used leaf springs and bilstien 5100's and threw some 35 inch tires under it. Initialy I only wanted a small lift but when I saw that it was goin in the direction it was going, I ended up with a 6 inch lift.
Anyhow, good luck with it and keep me posted as I'm curious what you will end up doing.