I would get them off line and then go to a local shop. You will be much happier. I have MAC offroad h-pipe and 2 chamber flows on my V6.
www.killercobra.com has a sound clip of mine. I would stick with the shorties because with LT on a V6 you may make it to free flowing and lose TQ and HP. Some people have had problems with MAC. My buddy and I have not. So what is better is a toss up.