I want to upgrade the Pcm now I have never done a compleate system upgrde and was reading that I need to reflash the pcm with the custom operating system and them the system will change but retain the original settings form the original system.

However I want to use say a 6L 2004 silverado operating system, or something better, 4.8L operating system on this suv. so how should I go about this swap so I don't need to cut and past every thing into the new operating system.

Any help would be grate thanks.