I have an '88 GMC 350 conversion van which needs a muffler again for the 5th time! Every couple of years, the muffler rusts out. Its a 3" inlet/outlet oval type (24"? long) muffler with a lifetime warranty, but they get me on labor each time this happens. The local shop quoted $300 over the phone for a stainless muffler which seems too much $. I want a muffler to be extra quiet and last, so performance is not necessarily a priority. Any recommendations? Thanks.