98 350 vortec swap

I some questions that hopefully someone could answer for me.I picked up a 98 chevy 3/4 van with 350 vortec. I would like to swap the engine to my 85 chevy 3/4 4x4. The frame is actually a 1980 with turbo 400 trans. and a 205 transfer case. What do I need to do the engine swap. Many people always say to get complete harness and computer from doner vehicle and it should be fairly easy. What about transmission plug, doesn't computer need to see this signal as my turbo 400 doesn't have this. Also could there be the possibility of using this 4L80E on my truck and tranfer case. I have spent much time on the net for info and have not found anything. Any help would be greatly appreciated.