I have a couple of dodgy 1.0 boards with nice cases, and a couple of clean 1.4 boards with dodgy cases. Can I just do a straight swapover of boards/cases? Can the power supplies stay where they are or do they have to move with the board?
Yes, you can swap your boards and cases. You need to swap power supplies too, because 1.2-1.5 boards use different PSUs than 1.0-1.1. But be careful when swapping 1.6 board to 1.0-1.5 case. You have to cut a piece from the bottom case: http://www.theisozone.com/tutorials.../16-xbox-will-not-power-on-fix-with-pictures/