Two things about the firebird switch...
The dimmer won't work with the Fiero... You could just swap the Fiero dimmer onto the Firebird switch, or move the circuit board of the Fiero switch over the the housing on the Firebird switch. You don't need the heat sink, you can throw it away.
The firebird headlight switch won't control the Fiero headlights unless you do one of two things... Either add a relay like shown here:

or add a wire to the "b" terminal of the Firebird switch.

Time for a shamless plug... I sell a 100% plug and play wiring harness for those that don't want to, or don't know how to mess with wiring. On sale now for $399. Includes all the switches and gauges modified to work in the Fiero.
Basic kit Includes $399
* Plug and play harness
* Firebird gauge cluster (120 mph)
* Firebird headlight switch
* Firebird trunk popper switch
Upgrades:
Digital Odometer +$50
Firebird Radio Harness +$50
[This message has been edited by jscott1 (edited 04-17-2007).]