There are some potential SID's (Supplemental Inspection Documents) that have been proposed by Cessna. This is an ongoing effort pushed by the FAA based on "Aging Aircraft", something all manufacturers will be facing. There is more information on the situation here
http://www.337skymaster.com/messages...ead.php?t=2513
If you study this thread it will help to define the process. For more information and if you really want to learn about Skymasters, join us in Dayton, OH on June 1 for the Anniversary Fly-in event.
The AD that is most current to this aircraft only pertains to those modified with Aviation Enterprises wing extension fuel tanks and winglets. If you don't own a Skymaster yet just beware of any modifications to the wings. Ask questions, talk to a Skymaster experienced owner or mechanic about these before proceeding.
http://www.337skymaster.com/messages...ead.php?t=2771
There is one other AD to have the spar inspected at 5,000 hours but this AD has been published for many years.
Hope this helps