Dimensions

I have a rather interesting modding idea rattling around in my skull, and, before picking up my Dermil, I would like to draw a few highly detailed designs, and design the tightest, smallest system I can, while keeping everyhting thermally stable.

Would anyone know where I can find RELIABLE dimensions for the Mac Mini, the motherboard off a Power Mac G5, those of a motherboard suitable for dual Xeon 800 processors, mini itx boards, X-Box motherboards, Playstation 2 innards, a game cube, the innards of a Beige Power Mac G3, and a quicksilver G4

Many thanks.