I own a 1990 3.1 V6 Firebird and I am swaping in a 5.7 350 but my question is can you use the V6 wiring harness on the 350 when I swap it in. I am going to change the MAF sensor to a MAP one and use the V6 ECM also. And put two more injector wires for the other two injectors will this work. Can some one let me know if this will work. John

 

NO, sorry that will not work--
two different animals(Engines)-- two different brains(ECM).
The easiest way to explain is to tell you to look at the manual and when you see all the different parameters, and systems etc... one big one is the 3.1 is CCC ingition and the 5.7 is distributor.
Just think if it was that easy the factory would have done it that wasy in the first place.
But it should be easy to find one of those used harnesses around maybe even a new one from Painless products inc.
But that isnt plug and play either you have to figure out at the bulkhead(firewall fuse feed) connector what wire goes where. Try and look at a factory manual for the car and the car the engine came out of to see what wire does what and go from there..Sorry to be the one to give you bad news..
But if you take your time and do the research it will be worth it.

 

As long as you get a 350 from a TPI setup...it's virtually the same wiring...A few splices here and there, and your all set...
Here are the differences between the 350 ECM and the 3.1

 

WOW! Two completely different answers. Thanks for both replies. I think that since we are also going to be changing the chip in the computer to a "proliminator" and load our own .bin that the computer issue shouldn't be a problem. And we are also getting rid of the EGR and its associated hardware as the Holley Stealth Ram doesn't have a place to mount one!!! Solves that part. My only concern now, is that the connectors used on the harness and the sensors are the same. Probably just take sensors off the 3.1 and use them on the 350 (if they fit). Appreciate the answers and the diagram of the pinouts on the computer.