The 4.1L Cadillac engine was an early 1980's design. If they were meticulously maintained and never overheated the slightest bit they ran fine but throughout its history it was plagued by leaking cylinder head gaskets that would cause antifreeze to get into the oil that destroyed the bearings.
If you are dead set in using this engine in a Fiero, a non ECM distributor, carburetor and new fuel pump/reg would be required to convert it to non-ECM use. That engine is now very old and 35 years later I would not expect much.
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Powerlog manifold, Northstar TB, LS1 MAF, 3" Flotech Afterburner Exhaust, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, HP Tuners VCM Suite.
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "