Check the buy/sell forum..about the only suggestion I have as far as acquiring the SVT header/cat. The header shouldn't be difficult to get, but that cat is kind of a problem. They are astronomically expensive new, and (I believe) most of us on here go the high flow cat or ORP route, as it's cheaper and better than factory parts.
As mentioned, if you passed emissions, you have the option of doing an ORP, but the car does get loud and raspy (just a forewarning). Also, you'll be stuck swapping a cat back on for emissions next time around (or getting an O2 cheater for the downstream O2 sensor, assuming you don't get a visual inspection done in TX at all).
My recommendation would be to pick up an SVT header used (I haven't been in the buy/sell forum for a while, but they used to pop up pretty frequently -- otherwise they can be had new for a price) and then get a high flow cat so you can stay emissions-legal.
If you're dead set on a factory cat, don't quote me on it, but I recall the stock cat being many hundreds of dollars...