With a proper tune you'll be fine. I know a couple guys around here with 2011+ GT's and a guy with a 2013 GT500 that have O/R mid pypes. The GT500 has long tubes. Its mostly the tune as most shops don't look under the car.
Yea I'm pretty sure they are the same. A lot of guys swap them out all the time. Especially the rear bumper so they can have their tails stick out under the bumper.