You will need to get an adapter from Marlin or Inchworm to mate to the back of your transmission to run a gear driven transfer case. These adapters are made to run a 23 spline transfer case, which was only found in the 86 an 87 turbo pickups. They are as rare as hen's teeth. You can buy the 23 spline input from Marlin or Inchworm and convert a 21 spline case, but it is only a little more money to just buy 23 spline low range gears (4, 4.7, or 5) from either of the above vendors.

Harry Wagner
Harry Situations
4x4Wire's Toyota Section