I think you would be surprised at how much these cabs and beds can move if they are rotted. So yes it is possible to see a noticeable difference between sides or ends of the truck. In looking through the various body manuals the Task Force and later bodies are quite a bit more complex than the AD's as far as panel construction. It may be worth your time to do some cleaning and detective work underneath/inside to assess overall condition. You may want to take a long hard look at the bed mounts as well.
