If you go flowmaster, get the 70 or 80 series.
I had a 40 on a ZJ with no cat, sounded OK but resonated badly at 30-35 and was a little hard to hear the back seat at hi-way speeds.
We did run a Dynomax muffler on the racecar, 2.3L Ford, looked like a glorified glasspack, but did like the sound.