That setup is probably the 4.5L engine and it came with a non-electronic 4T60/440T4 transmission. If the swap is done using the original ECM all should work fine. The only drawback may be that this engine / trans combo will require nearly the same work as installing the 4.9L/4T60e. powertrain that has far more horsepower. The OP said custom installation, so if its not Fiero the answer may or may not be here. I would advise the op to use the ECM that came with the engine for better drivability, mileage and TCC lock function. It should be possible to use a powered switch to lock the TCC but you won't gain anything so why do it?
------------------
" 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.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "
