The title says it all! Would any mechanics on here know if a dual out '07 exhaust for a 3.9l engine on a coupe, work on my car...a '08 3.5l engine coupe?
I really want dual exhausts but can't find a single "kit" for my car...it's all single output exhaust. I found a 07 dual exhaust for a 3.9l engine...but I'm worried the engine size might make or break it for me!

The problem there is that 2008+ have a third cat and the flange is different. Will it fit - yep . Will it be legal - nope.

what if I bought an extra cat?? Then would everything be fine? is all the dimentions the same??

The 07's have a different style flange and the hangers in the tunnel are not only different but are in a different location. You could still use an 08 on your car, but it will require a few cuts and welds to make it work.