4l60 to 6l90 trans swap in 08 sierra, where to start?

I am looking to get started on this trans swap for my 08 sierra 1500. the parts side im not worried about its the computer side. is the trucks computer able to be flashed for a base 6l90 tune and i would be left with harness work to go from the computer to the 6l90 or is this just a no go all around?

(edit- i know the engines computer doesnt control the 6l90, the 6l90 has its own internal computer. more less can the trucks ecm be flashed to communicate with the 6l90 tcm?

http://www.ls1truck.com/forums/power...0-a-print.html

This guy did it, might see what's needed. I glanced through, according to the thread you have to buy a new ECM because you'll brick yours if you try to flash in the 6 speed.