have a look here
http://www.camaros.net/classifieds/ ,they've recently changed their classifieds format, old ads can be found @
http://www.camaros.net/classifieds/index1.shtml
also check
http://www.fbody.com/cgi-bin/partsfs/postform.cgi
i found lots of back seats a on camaros.net a while back when i was searching for front seats.