I got a kit for pretty cheap on eBay over a year ago. It consisted of re-indexed torsion keys (like these:
http://cgi.ebay.com/ebaymotors/GMC-C...QQcmdZViewItem) and all the necessary rear hardware, specifically add-a-leafs and U-bolts. The U-bolts didn't fit, and neither did the stock shocks when I was done. Instead of being 2-2.5" of lift, it was more like 3-3.5 in the rear. Thus my truck still has a bit of a rake on it.
Personally I don't like the kit at all, and am looking to go 4-6." You can have my old kit, minus shocks, if I get a newer kit. I'm not budgeted for one right now, so it may be a while before I can do anything.
I originally bought my kit from a place called TFES Performance through eBay, found at
http://stores.ebay.com/TFES-Performance
It doesn't look like he sells those kits anymore, but he's got a few others listed. The guy is an independant seller, but he was *great* to me and he worked with me through any troubles I had. He was even willing to give me a walk-through installation over the phone if necessary. I'd highly recommend buying from him if you wanted to get something off eBay.
I have before and after pics of my truck if you're interested. Before, I had oversize tires and torsion bars maxed, and still rubbed the fender wells. Afterwards, aside from a stiffer ride, no problems.