Now seems like as good a time as any for the first post. I have been lurking here as I am thinking of purchasing an 80. I currently drive an 09 Tahoe that has a 6l80e trans and it is mated to a 5.3l engine. So it is not necessary to have an LS2 or LS3 if you want the 6spd trans. As stated above the 6spd is more high tech and is controlled by a TCM chip that is embedded in the trans. So the ECM and TCM for my model are separate where as I think older models with the 4spd were both controlled by a single removable PCM chip. Tunes are flashed to both the ECM and TCM separately with a hand held device. That is my experience and understanding of the 5.3l and 6l80e. Some others might have more insight than I though.