ok why is it you can't get the 8" radio set up in a reg cab but you can get it in an extended or crew cab? map, back up camera I would definitely like to see in a big screen and not that 4.2 . so when you get the better upgrade they say reg cab gets this this and this but the other cab config. get the bigger screen but it's seams to all be the same price and not any price cut for getting a 4.2 or am I just missing something when I go to the build it page on chevy?