Our newest came out of Oklahoma, I find most of them west of the Mississippi. There are two very clean (from the photos) close to each other in Oregon with mileage in the 80s. There are 9 4x4 6.2 Sierras for sale across America right now on Auto Trader with 85K to 197K miles.
The Oklahoma truck averages 13-15 mpgs per tank running around town, better than my Yukon XL with the 5.3. The lifted truck averages 11-12 running around town.
No AFM, these are L9H motors and the Sierra Denali uses it too.
This one is an NHT with 3.73 gears and a payload capacity of around 1800 pounds:
This is an All-Terrain with 3.42 gears: