Sorry for double post, dont know how to edit the title.
ANY ONE KNOW IF IT IS PREWIRED

 

Yes. I had a stock CD deck in my 06 GT and was able to swap it out for the Shaker 500 myself. The plugs are directly compatible. The only issue is that if you didn't get the shaker to begin with, you won't have the bigger speakers in the doors nor the subwoofer in the trunk. The sound defintely is better with the 500 even with my stock speaker setup. You may have to be careful not to crank it up too far since the stock speakers may not be able to handle the wattage.

 

Did you do a search?

I've read many times that if the car didn't come with the Shaker, you just can't add one. But I do remember a thread somewhere here where a guy got the whole thing, wiring and all, from a wrecked car and was gonna retrofit it.