Tator,
Do a search for "Yakima Q Towers" and you find numerous threads detailing the use of the Yakima system. I've got it on mine and couldn't be happier. Here?s one of those thread that details the cost of the system. http://www.chevyavalanchefanclub.com/cafcna/index.php?board=119;action=display;threadid=15302;start=0
Before I did this I permanently mounted the Yakima Tracks on the roof of my AV in lieu of the OEM racks. While I like it better than the OEM I rarely use it anymore now that I?ve got the Q Towers on the bed panels. It?s just too big of a pain the get the bikes on and off the top of such a high vehicle.
If you?re planning on only carrying bikes you might also want to check out the ?Sportworks TranSport Series racks feature our secure and convenient Ratcheting Quick-Load system (RQL). Carry up to 4 bikes with a 2" hitch. This rack folds up for storage and down from the vehicle to gain rear access while loaded with bikes.? It?s very convenient to be able to simply drop the bikes in the trays and ratchet it down without having to take off the front wheel. Here's a link, http://www.sportworks.com/sttra.asp