Could have saved you some hassle on the muffler, Vibrant makes a very nice 3" in, dual 2.5" out universal muffler. Used this when I switched to a stock looking muffler years back.

I wanted as stock looking as possible, the Vibrant muffler size is very close to the stock size, they sell tips that are the same size & slant as OEM, had these welded on staggered just like the factory setup, then bead blasted the whole muffler to ditch the polished SS for a nice satin finish. Have had DSM owners not realise it wasn't a stock muffler