EVAPORATOR CORE: Two air conditioner evaporator cores were used in the Fiero, one in '84 and one in all '85-88 Fieros. This evaporator core is unique and not used in other cars. As far as we have been able to determine, aftermarket units are no longer available and the best recourse is a used one. Fortunately they do not wear out often.
For the record, the '84 Fiero used GM Part No. 3054185 (AC Delco 15-6398). The '85-88 Fieros used GM Part No. 3090045 (AC Delco 15-6544 or Delphi EP1054). You may get lucky and find one under one of the above numbers.