The search feature of this forum will provide answers for about any question you have. There is probably not a question about the Skymaster that has not been asked on this site. Saying that it is always good for others to see some of the interest that new buyers have to spark their passion.
Wing AD
http://www.337skymaster.com/messages...ing+inspection
http://www.337skymaster.com/messages...ing+inspection
http://www.337skymaster.com/messages...ing+inspection
http://www.337skymaster.com/messages...ing+inspection
http://www.337skymaster.com/messages...ing+inspection
I am not aware of any mods to eliminate the inspection. There are a few air frames out there that are in the ball park for hours and only a dozen or so that are over the hill. It's not a big hour aircraft. The H model did not require the inspection as Cessna must have caught on to the issue and remedied. The H model is known as the best but it really depends on what you are doing and what's the mission. More on that H model in other answers.