you can take the seriel number of the stero to holden and thay should be able to help you
or if the stero is stantard to the car take the vin number to holden and again thay will tell you with no problems
my misses car has velocity 6' splits with cross overs and tweeters in the front and 6' 2 ways rockford foscate in the back doors
it sounds great of the standard deck but will sound sick when i fit a new deck
the main plug behind the dash you can wire it in to there. its a brown wire on one side of the plug i had my msd shift light wire in to it and it work great