Power supply is definitely different. You will need the correct power supply as well as the motherboard (or at least the ability to mod a powersupply, don't know much about that but some people have tried this route) As far as the power/reset button connections, they should be the same, I would think.
PB G4 15" 1.2ghz - Pismo G3 400 mhz - iBook G3 500 "Jukebox"
"SawSmurf" G4 500 - Quicksilver G4 Dual 1ghz modding...