I would assume that you wish to use a different bolt pattern wheel on your Fiero. It certainly can be done but you will need to consider the backspace/offset of the new wheels being used, their overall width, and the fit within the wheel houses on your car. Different wheels also have different wheel stud requirements and hub concentricity must be considered. Spacers also change the wheel alignment so that needs to be considered as well.
Point is that this is not a "one and done" job.
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "