Hello, this is my first time posting in any message board.<P> I have a 85 F250 2wd with a 300 6cyl and 4sp. It runs great but the cab is coming apart and the wires under the dash are a mess.<P> I plan to put the cab from a 84 F150 Larriet on and get ride of most of my troubles. All options are the same on the two trucks as far as I can see other than the 84 Larriet has a small v-8 fuel injection and my 85 F250 has a 300 6cyl with carb.<P> I'm not too worried about the engine compartment differences, but if anyone reading this can see a train wreck about to happen in my engine compartment, please tell me! <P>My main question is about the "brain box" or computer and the wiring harness that goes to it. I understand that the computer is under the dash and that the v-8 has a different computer than the 6 cyl.<P>are they different/do I need to swap computers? <P>If so, can I just put my computer from my 6 cyl into the wiring harness from the Larriet with the v-8. <P>Does the v-8 wiring harness have the same plug for the computer as my 6 cyl?<P>If I do have to do all that, do the wires in the Lariets computer harnes go to similar places as my 6 cyl harness, so I can get it all running OK?<P> Any one done this before and know if I'm opening up a big mess?<P> I'm not concerned with the rest of the change over, I've taken apart literaly 1,000s of ford truck bodies and put dozens back together, so the heavy lifting doesn't scare me. Just this specific wiring/computer question. Thanks everyone. Mike

 

The computers are TOTALLY different, and so is the wiring. You really need the right harness for the cab OR the right engine. All things considered, I'd recommend putting an EFI into the truck. I've investigated a lot of what you asked, and I ended up putting a '95 4.9L into my truck. You can see what I did in my signature link.

 

I'm with Steve, you need to go with a cab that is carborated, or convert to EFI. I stay with a carb'd cab myself, but steve likes EFI a lot

 

Your 6 shouldn't have a computer at all, just electronic ignition, unless your F250 is a sub 8500 LB GVWR model, and, an 84 with a 302 should be carburated, EFI started in 85. Are you going by the build date for the model year? They are not always one and the same.
You are overcomplicating your situation, the engine harness contains all the wiring for the computer and EFI system on the 85-86 EFI 302 trucks(and the 83-up feedback carb trucks too), not the cab harness(from what I have seen anyway.) The engine harness unplugs at the drivers side inner fender, and, should be a plug in, some of the EFI trucks had one connector wired differently, but a a test light and a generic wiring diagram for the Duraspark system will get you through it easy enough(this difference is NOT shown in the Haynes or Chiltons manuals I have seen)
Good luck
Evan