I'm not sure if I understand. Are you asking how to change the mounting hardware or are you talking about the picture appearing on the tube.
If it's the former, then a picture might help and people can look at how the mounting hardware is attached.. If it's the latter, then I'm not sure you have to do anything on the hardware end of things. You just need to send it the signal for the horizontal game, right? My horizontal monitor can display games in any orientation I want.