You would probably be better dropping it down to a 2.25 which if memory serves is the exhaust outlet size on the regular lo-po stock exhaust manifolds.

Get the longest muffler you can. Larger mufflers reduce noise more. If you get a regular oval style chambered muffler, get an offset in/offset out. Center inlets or outlets restrict exhaust flow considerably unless the muffler is a straight through design like a dynomax ultra flow.