I'm swapping my '90 305 TBI motor for an '87 350 TPI motor. I have the engine built and I have the wiring harness, but will the '87 wiring harness hook up to everything my '90 harness hooked up to? The accessories hook up fine, but I remember reading or hearing something about where the harness needed some adjustments. Please inform me if you know. Thanks a lot.

 

You may have some "challenges" like alternator and AC if you keep the accessory drive setup from the '90.

I discovered that an '87 LB9 AC had a different high side switch than an '86 LG4, even though the drive setup was identical. Go figure. Couldn't get the switch to come out of the '86 compressor, so had to go buy one. But, at least it fit in the compressor the same way.

 

If you have the wiring harness for that engine, you should have no problems.

 

an 87 and a 90 have the alternator and A/C compressor on opposite sides of the engine bay. So depending on whether you use the serpentine setup from the 90, or V-belt from the 87, and which harness you use, you may have to lengthen and shorten some wires.