A muffler that works in the stock location with minimal modification-slightly
larger muffler straps and use of a three bolt flange rather than the included
two bolt, is the DynoMax Super Turbo muffler.  The cost is under $59 and
comes with a lifetime warranty.
Has less back pressure than stock.  This allows the engine to put more power
into driving than forcing the exhaust out a restrictive muffler.

Add a single Monza tip and the exhaust sound is cool.

While driving I barely hear the exhaust noise.  I even removed the bed
cushion and the carpet and the exhaust noise is still barely heard or even
the engine noise.
I like the quietness and the added power from the muffler.

Robert