you need all the harnesses that come with the ps2 3 volt kit which they don't sell anymore as far as I know and the harness comes with tac board and tac mounting hardware 2.4 volt battery and battery harness and 4 ohm speaker, maybe an asc tech might have one. good luck. why don't you just install a ps3 kit they come complete with everything you'll need?
I'm not sure if you can use the ps2 slave board with a ps3 kit maybe a asc tech will chime in here!