you mean a stock one or U/D one. the stock one is the old style, meaning it's compatable with any mid 01 or earlier 4.6L. the bullet u/d pulley kit is the same as the 96-99 cobra's and the only change in the 96-mid 01 gts to 96-99 cobras U/D kits is the alt. pulley.
maybe more info than you are asking but i hope it helps.