i tell ya David if i was looking for a fiberglass truck body or some sort of lighter weight composite material..i would go looking in the Round track world..they have many bodies sitting around that they update each year from the craftsman series to many other divisions that runs these trucks.
i have seen them really cheap at the annual Lowes Motor Speedway swap meet each year..
its not a prostock design but can be made to work ( bolt on any type chassis)..they do have the dodge bodies available..
just an idea
look at this 1st pic of the dodge body..wicked looking..
http://www.autoracingtrader.com/race_trucks.htm
Brian