Yes the Trucks show on the Powerblock on the Spike channel had a few good episodes on their '66 C10 build. They started with a long bed and made a shortbed out of it.
http://www.powerblocktv.com/site3/index.php/watch-full-episodes/ep?ep_show=TK
I can't remember the exact episode that they did the shortening but if you could find it, it would answer most all of your questions