Unfortunately it isn't 1984 where everything is plug and play. While I'm no engineer/master tech/etc, I'm sure there is an ECU connection somewhere that lacks in the 4runner. You mentioned it does have a manual, that tells me you would have to rig up a lever in the cabin (cutting/welding/etc).
This is probably why no one has attempted it. Doesn't sound like it's worth it.
link to more info:
4th Gen 4Runner with a GX Transfer Case - Toyota 120 Platforms Forum