I have an '09 LT with 3.5, and I bought the Magnaflow catback exhaust. You will need to buy the driver-side hanger that bolts to the frame (kinda under trunk). You unbolt the factory exhaust at the rear of the cat, and everything else is held on by rubber hangers. Im pretty sure that The exhausts all follow the same Patterns on for the 8th gens, and the magnaflow kit bolts together and also follows the same path and hangs on the factory hangers. The kit is made from stainless steel, so it will last longer than the rest of the car!
It only took me about an hour to complete the swap. And you get a little better fuel economy and a little more fun to drive.
I can't remember the part numbers off hand, but I can look at my invoices and get the Chevy and Magnaflow part numbers if anybody wants them. If it's not raining tomorrow, I'll snap a picture.