Remember that there are two types of systems in the 5th gen Camaro, ie Base System and Boston Acoustics Premium Audio System. If you are wondering if you have the base or boston stereo, there are a couple indicators. On the Boston system, the front door speakers have the "Boston" emblem in the middle of the speaker grille. Also the boston 6x9 rear speakers will have four wires going to them instead of two. As for locating your boston amp (if equipped), it is located on the back wall of the trunk on the left side behind the moulded carpet, ie inside the drivers side tail lights.
Base System: Really the only option you have is to splice into the rear speakers using a loc (line output converter). If the head unit has been changed, then it is very possible to run rca cables and your turn-on lead to the rear.
Boston Acoustic System: The absolute easiest way to accomplish this in a boston equipped car is to use our Exclusive T-harness adapter (part# 5G-X3RCA on our website)
also seen in this video
The harness was developed by yours truly to take the guess-work out of tapping into the wiring bundle on the Camaro. All you do is plug in our harness into your amp and it gives you 4-channel rca signal as well as a 12v turn-on trigger for your aftermarket amp. The best part about this harness is that you don't have to know anything about wiring or wire colors or splicing wires or soldering or anything of that nature. Think of this harness as 'putting rca jacks in your trunk' so you can hook up your amp. Now the harness will not power your amp. You will still need to run power and ground cables from your battery. But your battery is right under the trunk floor, so it couldn't be any easier. Just make your connections. Add an in-line fuse on the positive cable as close to the battery as possible. Some will say don't ground to the battery and that a chassis ground is best. But I have grounded many amps to the battery without any issues and in the Camaro, it is easy, so I highly recommend it.