If your looking to replace resonator or just the muffler, you have to look for 1.75" inlet hole. If your thinking of upgrading your exhaust completely, your best bet is to find a SVT exhaust from, you guessed it, another Contour SVT, replace the muffler/resonator w/ one that fits (2.25") of the brand you like.
Definately check out the Exhaust Database for suggestions. Unforunately you may have to increase the size of your pipe in order to find something that fits. On the bad side, it cost a bit more money, on the good side, you get a few more HP out it and a nice growl to your engine.
Its up to you, "the power is yours." - C. Planet