hey guys i just picked up an 85 iroc z... ok lol i hate 5.0s thats all ive had in the past . any way i have a chance to pick up an 87 gta TA hit in the side with 89 thousand miles on it... it has a strong running L98 in it with a good tranny.. and it just so happens the 700r4 is gone in my car and in need of a replacement ... will this complete engine just drop in and be able to work with the wiring that i already have there for a lb9 5.0 tpi engine i realy want this to be a plug n play swap... i was thinking all id hae to do is take the 350 chip out of the gta n put it in the computer in my 85 5.0 computer ... let me remind you both cars are tpi and have the older style heads along with mass air flow sensor...so i assume it should work or should i just put the gta computer in my 85 iroc...please help me out guys...

 

That's a puzzler. GM made running changes to the electrical system thru the years.
The 3 things that come to mind are the speedometer pickup, chercoal canister, and the 9th injector. I don't know what years they had the 9th injector and when they took it out. The early models 82-? had cable speedometer and later ones used an electrical pickup. Both of these changes meant a different ECM.
Here's an idea: What if your question was:
Can I swap in an 87 TPI engine+transmission, engine compartment wiring harness, and ECM&harness into an '85 TPI car?
The only way to be sure (short of just trying it) would be to buy the factory schematics for both years (about $10 each), sit down and compare each wire.
Most of the changes were made "backward compatable" so they could use up leftover previous year's dash wiring harnesses with a new engine harness.
This means that a wires from the dash harness to the ECM harness would be in the same location with 2 different engine packages.
Personally, I think it would work if you left the engine harnesses plugged up on the engine and moved the harnesses and ECM together into the 85.
You may want to try a search in the engine swap forum. They may shed a little more light on what years, what changes were made.
My . (better than no repy, huh?)

 

Check the part numbers on the ECM. If they are the same...... should be golden. IF not, gonna have to do some research.

 

It may sound like alot of work but it really is not

take the whole harness dash and all and put it in your ride