While you might find individual parts that *could* be used (with lots of work), it's not a project undertaken lightly. You'd be looking at a significant custom fabrication effort, potentially including:
* Custom brackets: You'd need to fabricate brackets to mount the Grand Am calipers to the Fiero spindles or hubs.
* Modified or custom rotors: The Grand Am rotors likely won't directly fit the Fiero's hubs.
* Brake lines: New brake lines would be required.
* Potential issues with proportioning valves: The braking balance between front and rear might need adjustment.
The effort involved usually makes pursuing other, more readily available upgrade options (like using a readily available Fiero brake upgrade kit from a reputable supplier, or using brakes from another GM car known for a better fit) more practical and less headache-inducing.