I found this thead in the "other" section. While it is not a FWC, it deals with how to change an older camper to fit a newer truck model. But more importantly it shows what you can do with the extra space in a new storage section. Pretty neat set up and worth taking a look.
http://www.wanderthewest.com/forum/topic/12409-restoring-a-68-siesta-pop-up-and-getting-it-to-fit-a-newer-style-truck/
http://www.wanderthewest.com/forum/topic/12409-restoring-a-68-siesta-pop-up-and-getting-it-to-fit-a-newer-style-truck/