The current issue of Automobile magazine has a brief write-up and pictures of the GM concept truck. It's got Fox Shox and disconnectable sway bars and some other stuff. They're showing it with the very heavy Allison diesel which I wouldn't expect they would offer if it ever makes it to production.
Looks good except for the massive grille up front. If you laid it down you could barbecue a whole cow on it.
Found online:
"This massive GM, set for the stage at the 2011 Detroit Auto Show, features a 6.6-liter 397 horsepower Duramax turbo-diesel V8 with 765 pound-feet of torque. The transmission is a six-speed Allison 1000 unit.
The Sierra All Terrain concept is shorter than a traditional HD Sierra, but features upgraded suspension with three-inches more clearance, a wider -- 73 inch -- track, front and rear jounce shocks, electronic disconnect stabilizer bars, composite underbody protection, 35" BF Goodrich tires on 20" rims and Fox shocks with remote reservoirs in the wheel liner."