The Mustang TB you need is the 96-02 4.6L 65mm. (I am pretty sure). So the one you posted probably will not work.
here is the how-to, once you find the right TB: http://www.focushacks.com/mod/SPI_-_...ied_Mustang_TB
try a search for more info.
also, check local junk yards, you can probably find it a lot cheaper....