The correct part number is "DF985985". Make sure you change to the viper master/slave because the stock hydraulics can't handle the the new stroger pressure plate.
Yes, your current slave is plastic and a pos, the viper slave is cast... You will need a 1/4" spacer behind the slave to make it work properly. Also a 1/2"-3/4" spacer behind the master so the pedal higth is correct.