Unusual option, a sleeper trunk.. I found a 68 Bonneville, and Dan at Hemmings came across a AMC Hornet

 above from a 2007 gallery I posted http://justacarguy.blogspot.com/2007/07/68-ponitac-fastback-is-rare-one-with.html

and this Hornet is from Dan at Hemmings Blog, http://blog.hemmings.com/index.php/2012/07/26/from-the-hemmings-nation-flickr-pool-the-hornet-hutchback/comment-page-1/#comment-4936631 and it is showing a Group 15 option, the 1973 Hornet Hutch Mini Camper Kit