heres a good site i found to buy mufflers from http://www.fle-online.com/
find out what size tubing you have, most likely for you its 2.25inch...but you might have 2.5inch...check to be sure
then decide whether you want dual-outlets or not....the Camaro mufflers mentioned will give you that.
Magnaflow has a really good choice of Universal fit muffleres....if you have the 2.25 tubing the 5x8 mufflers offer a good selection of replacements.
if you have the 2.5 inch tubing, the 5x11 may be your better choice, that is of course if you even want a Magnaflow....Magnaflows appear to be quite alot cheaper(at least on that site anyway) and based on the article in the Exhaust thread they outperform Flowmaster anyway.
2000 Oldsmobile Intrigue 3.5L DOHC V6 15x,xxx miles "The Forgotten W-Body"
shaved badges, Eclipse HU, Pioneer TS-A1370R'*, Pioneer TS-A6971R'*, 20% tint, cleared corners, Silverstar Hi'*, 9005 Low'*
Fenderwell Intake, Hi-Flow Cat, U-bend delete, GMPP Handling Kit, MOOG endlinks, and 12-inch front rotors
1996 Bonneville SE RIP 157,751 miles, totaled 8/29/05