Anti-lock brakes comes on and brakes are hard as a rock what is causing it

Believe you have the Teves ABS system as most Fords of that era did, there is a pump motor that pressurizes the brake fluid and stores it in an accumulator. Two things may be failing here; the accumulator, or the pump motor. Both can be tested but you should look up the process in an older repair manual for your make and model, or ask around on any Ford forum for the procedure to test these. (I suppose the ABS computer could be another faulty part). The easiest place to start is making sure all ABS fuses are good and well seated in their sockets, and wire harness is good without nicks or brittle connections. Replacement of the whole system can be very expensive, and used parts in scrap yards scarce. Swapping out to a non ABS system is another option but that should only be done by an expert.

First answer is correct.