my 87 v6 auto has cam ,headers.4bbl carb,hei ignition, but now have no signals for trans,tps,o2,maf,etc. couldnt i swap an early 80-82 thm125(pre electric)

maybe.

no ECM and sensors for it mean TCC won't lock eating more fuel and be hotter because unlock TC is a big heat generator.

No/Wrong TV cable setup is bad too affecting gear vs engine load etc.

Non TCC version of TH125 still wants TV cable correctly set too even if changes TC to generate less heat and less torque boost to do that.

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

If you decide to upgrade and use a 4T65e (that gives you four speeds) you can bolt in and shift that transmission using a Compushift transmission controller.
Compushift Trans Controller

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" 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 "

[This message has been edited by Dennis LaGrua (edited 11-19-2019).]