Wiper motors in the Fiero differed depending on the "intermittent" or "pulse" action.

'84: Accoring to the Hollander manual, the'84 Fiero did not have a pulse wiper. However Jim Teague, the original owner of an unmodified '84 Fiero, advises that his car has an intermittent wiper motor. So it appears at least some '84 Fieros came from the factory with the upgraded motors. In any case, the cars below had wiper motors which can swap with the '84 Fiero:

Blazer/S10/GM Jimmy S15   '83-84
Blazer/S10/GM Jimmy S15   '83-93  without pulse wiper
Buick Skyhawk             '82-83
Buick Skyhawk             '84-89  without pulse wiper
Cadillac Cimarron         '82-83
Chevy Cavalier            '82-83
Chevy Cavalier            '82-94  without pulse wiper
Olds Firenza              '82-83
Olds Firenza              '84-88  without pulse wiper
Pontiac 2000              '82-83
Pontiac 2000                 '84  without pulse wiper
Pontiac Astro             '85-89  without pulse wiper
Pontiac Safari (GMC)      '85-89  without pulse wiper
Pontiac Sunbird          ' 85-94  without pulse wiper
S10/S15/GM Sonoma         '82-84
S10/S15/GM Sonoma         '85-93  without pulse wiper

'85-88: with pulse wiper. Those without pulse wiper had the same motor as '84.
Buick Skyhawk             '84-89  with pulse wiper
Cadillac Cimarron         '84-88
Blazer S10/GM Jimmy S15   '85-93  with pulse wiper
Blazer S10/GM Jimmy S15      '94
Chevy Cavalier            '84-94  with pulse wiper
GM Syclone                   '91
GM Typhoon                '92-93
Olds Bravada              '91-94
Olds Firenza              '84-88  with pulse wiper
Pontiac 2000                 '84  with pulse wiper
Pontiac Astro             '85-89  with pulse wiper
Pontiac Astro             '90-93
Pontiac Safari (GMC)      '85-89  with pulse wiper
Pontiac Safari (GMC)      '90-93
Pontiac Sunbird           '85-94  with pulse wiper
S10/S15/GM Sonoma         '85-93  with pulse wiper

'84-88: If you transfer the wiper circuit board in your Fiero to another motor, you can use wiper motors from any of the cars below in a Fiero:

Buick Skyhawk 1.8L             '84-86
Buick Skyhawk 2.0L             '84-89
Cadillac Cimarron 2.0L         '84-86
Cadillac Cimarron 2.8L         '85-87
Chevrolet Astro Truck 2.5L     '85-90
Chevrolet Atro Truck 4.3L      '85-93
Chevrolet Cavalier 2.0L        '84-89
Chevrolet Cavalier 2.2L/3.1L   '90-94
Chevrolet Cavalier 2.8L        '85-89
Chevrolet S10 2.5L/2.8L        '85-93
Chevrolet S10 4.3L             '88-94
Chevrolet S10 Blazer 1.9L      '84-85
Chevrolet S10 Blazer 2.5L      '85-88
Chevrolet S10 Blazer 2.8L      '85-90
Chevrolet S10 Blazer 4.3L      '88-93
GMC S15 1.9L/2.2L              '85 
GMC S15 2.5L/2.8L              '85-90
GMC S15 4.3L                   '88-90
GMC S15 Jimmy 2.5L             '85-88
GMC S15 Jimmy 2.8L             '85-89
GMC S15 Jimmy 4.3L             '88-93
GMC S15 Sonoma                 '94 
GMC S15 Sonoma 2.5L2.8L/4.3L   '91-93
GMC S15 Syclone 4.3L           '91 
GMC S15 Typhoon 4.3L           '92-93 
GMC Safari                     '93
GMC Safari 2.5L                '85-90
GMC Safari 4.3L                '85-92
Oldsmobile Bravada 4.3L        '91-94
Oldsmobile Firenza 1.8L        '84-86
Oldsmobile Firenza 2.0L        '84-88
Oldsmobile Firenza 2.8L        '85-87
Pontiac J2000 1.8L/2.0L        '84
Pontiac Sunbird 1.8L           '86
Pontiac Sunbird 2.0L           '85-94
Pontiac Sunbird 3.1L           '91-94