I have an old Apple TV that I have hooked up to my 4:3 TV, and I would like to have the output from the Apple TV match the ratio of my TV so there isn't any stretching or squishing. It's running the latest firmware 3.0.2.
I don't believe it will be 4:3. One of the requirements for ATV was a widescreen TV. I think it always assumes a 16:9 ratio. As @matthewpavkov suggested, best bet would be to get the tele to force the input into 4:3, but it's very model dependant if the tele actually supports that.
Update: I stand corrected, there seems to be a thread related to this exact issue on the MacRumors fourms http://forums.macrumors.com/showthread.php?t=658621 However, it seems that it stopped working on the 3.x firmware, so there's an even more hacky way of achieving it here. Sounds horrible though! http://forums.macrumors.com/showthread.php?t=811425