SEAT RETAINING BOLTS "FELL OUT" WHILE BRAKING FOR MAJOR ROADWAY. SEAT PIVOTED ABRUPTLY TOSSING DRIVER INTO STEERING WHEEL AND ONTO FLOOR. DRIVER STOPPED VEHICLE WITH HAND ON BRAKE WITHIN A FEW FEET OF A PASSING SEMI-TRAILER TRUCK TRAVELING AN ESTIMATED 60 MPH. A FRACTION OF A SECOND LATER AND FATALITIES WOULD HAVE BEEN CERTAIN! THE SEATS ARE PART OF A MARK III CONVERSION. THE RETAINING BOLTS APPEAR TO BE FASTENED WITH ALUMINUM WASHERS THAT OBVIOUSLY DO NOT HOLD UP WELL. THE SEAT HAS BEEN REPLACED; HOWEVER, I DO NOT KNOW IF THE DEFECT HAS BEEN APPROPRIATELY RECTIFIED.