You can change the roof panel to one that has a factory sunroof in it very easily.
The space frame of every Fiero already has the hole and mounting points for a factory sunroof. You will need to remove the factory sunroof panel off of the donor car. You will need a piece of wire about 36" long as well. The basic way to swap roof panels is to first remove the wipers and lower windshield panel, remove rubber trim around windshield, Remove interior headliner and the four 13mm nuts that hold the roof down.
Now the very tricky part, You need to take a long piece of thin metal and carefully push it between the roof and frame towards the windshield. There is a tar seal strip along the front of the roof above the windshield. You can "cut thru it with a long blade but it is best to use a blade to push thru then slide a piece of wire thru and "saw' thru the sealer with the wire. Once it is loose, DO NOT LIFT THE ROOF OFF YET. Take the a flat blade screwdriver and start popping the roof off at the bottom of the windshield. Just move it up enough to losen it. You need to do this slow and careful. The part of the roof that goes down the side of the windshield is VERY THIN and can break easily. Once it is all loosened carefully lift te roof off.
Then when you install it on your car, carefully lower it down and carefully seat it down. Once the bottom edge is seated you can bolt the roof down from the inside and install everything else you removed. Total time to swap roof panels is about 4 hours.