http://ipodcarparts.com/chevroletgm-...ary-p-291.html
There is another site, and it's in the forums somewhere but I have to search for it.
EDIT: Found it here. http://www.tamor.org/forums/showthre...highlight=ipod
The link is busted, but I think this one will get you where you need to be.
http://pac-audio.com/productDetails....&CategoryID=36