Flowmaster Tips are 3 inch I beleive...I have a brand new extra set Flowmaster 3" tips that came with a tailpipe kit I bought. The hangers were meant for a 99-04 V6 bumper without cutouts though, so they are too long for a GT bumper, but can be easily modified....
If you're not stuck on the brand name, Summit has rolled slash cut tips like on the Mach 1s but 3.5". They won't be bolt on but a mom and pop's muffler shop can weld them on for $50 or less.