1999 blazer transmission swap with a 1996
 

I was wondering and from the looks of it I can not swap out a tranny out of a 1996 blazer 4.3 4X4 with a tranny from a 1999 blazer 4.3 4X4. But what if I swapped everything motor tranny and transfer case at the same time and I guess the ECM or PCM as well. Can that be done? Or would there be other issues as well. If anyone has some ideas your input would be appreciated. Thanks