Im planning on geting a new muffler for my truck with the 6.0. I want to keep it all stock with same pipes and cats. My question is what offset do I need the new muffler to have? Im planning on a Thrush 17649 Welded Muffler since im on a high school senior budget, and I know its not the best out there but its cheap and should get me through until next summer. Also about how much would it cost to have just the muffler installed?