I'm not sure a 1996 has OBDI or OBDII, very close to the introduction of the later. From what your describing it sounds like OBDII. If so, I would say that your catallytic system is warranted for not 5k, 7k, or 8k but 80k. You should still be covered and not have to pay a dime. You can do either of the following, hold your ground that the system is warranted for 80k and have the dealer call ford for verification or, you yourself call ford and get the confirmation number (if available). I wouldn't pay anything until you find out for sure that your liable.
Good luck
