I also have a C2500 & thought of shortening it after seeing the "Gearz" tv show. But, then I thought about GM not building a short bed 3/4-ton truck. I've decided not to shorten mine after all, but your truck is your truck. Do with it as you wish. Here is the link (1 of many) for the episode of "Gearz". There is another episode broken into many parts showing him assembling a short bed from LMC.
https://www.youtube.com/watch?v=O9zy08qsahk