1991.4runner

I'm researching the swap to 4wd, presently I'm 2wd. Most threads aren't really clear in the transfer case wiring needed. Do I need to get a computer and wiring from a donor to make the transfer case work? Or can a few wires simple be added to the current harness?

1991.4runner

Or Is there less wiring if a gen 3 transmission and transfer case can be swapped in? They look like they have no/less wiring for the transfer case.