Here is the link to a bunch of info, in it they talk about duramax and when it's coming out
http://www.amghummer.com/features/gossip/gossip.htm from what I think, 2 cents, the heavy duty option will be in the $25k to $50k range. You will get a lot of stuff( HD-package) hd brush guard, towing package, winch, off road tire package, allison is around $8,000 option for silverauto you can get now. Also get the Duromax as an option for about same amount. I here the allison will downshift going down hill and when you use your breaks. anyway it does a lot more then just being a transmission.