american muscle has a accufab for 349 and they say it fits the 96-98 cobra and 01 bullitt...

 

summit has a bbk for 320..I just typed in 01 mustang and it came up they have a twin 62 or a twin 65..hope this helps

 

Try eBay or the classifieds as there isn't much that could be wrong with a used TB. Why are you looking for a TB anyways? Sounds like you think there is something wrong with yours?
I have the SVO intake and one of us has an intake that will accept a single oval blade TB so you might want to find out if that is you for an extra piece to look for. Good luck and what else are the car's/motor's symptoms? Maybe you don't need a TB as I said not much to go wrong unless it was tossed about!

 

Definitely go with the 75 mm.

 

I dont think they make a 75 in a twin design..Highest Ive seen is a 65