Get the longest case Dynomax Super Turbos you can fit. They will be the quietest.
BTW, if you have 3" or larger tails, you're simply NOT going to have a quiet system.
https://www.youtube.com/watch?v=PMunVfwROfk -Super Turbos
https://www.youtube.com/watch?v=ly5IlDyXFbo -Goerlich Xlerators