87 vs 89 wiring harness

[Optima Bill]

Well, I have found out the hard way that the two years are not interchangeable. I have the 89 engine harness on the 89 engine but it will not plug into the harness/fuse box at the dash connection point. So now I am at a crossroad. Do I swap the 87 harness onto the engine or do I swap the interior harness and fuse box? I am putting the 89 frontend on the 87, but if I retain the 87 wiring, no big of a deal to change that harness a bit for the proper connection changes at the lights. I am just wondering now if the 89 computer will work with the 87 harness. All the connect points on the motor are the same, but since they obviously changed the harnesses, not sure they all mate up on the computer right if I don't swap out to the 89 all the way through the truck.
Am I overthinking this? just swap the engine harness back to 87, make the small changes on the headlight harness and move on?
Thanks guys.

 

[blazinzuk]

yah man you are over thinking, they changed stuff year to year so you are going to have change a couple things but it shouldn't be too big of a deal.

I would use the 87 harness and switch the headlights over

 

[Optima Bill]

Thanks Eric, so you are saying the interconnections should be the same as far as gauges and computer connections go? Certainly a lot easier to change the engine harness and from what I can tell both are the same except for the main plug into the fusebox.

 

[blazinzuk]

Thanks Eric, so you are saying the interconnections should be the same as far as gauges and computer connections go? Certainly a lot easier to change the engine harness and from what I can tell both are the same except for the main plug into the fusebox.

I cannot tell you for absolute certain but between an 89 and an 87 what you mentioned should be the same.

I know I can plug my computer plug into a 91 TBI computer from a caprice so I bet they are the same.

Of course nothing is certain in these trucks, I had all sorts of weird little stuff on my 73 that only happened in that production year, and only early in the production.

 

[blazinzuk]

I could go out and look I suppose I have a parts 89 and my wheeler is an 87