Building lost cause 86 into 89/90?

I have an 86 Pioneer. The interior is straight, and that's about the end of that. I've got clear paper on it, and it's not a major collision victim. It has the little V6 and three speed, vacuum selec trac switch in the console, and CV joint front end. At least it doesn't disconnect, I guess. I want to have the 4.0/AW4 and NP242.

My donors are an 89 Limited and a 90 Laredo.

The 89 has already donated the transmission, case, axles, shifter, linkages, and drivelines to my 96 which came 2wd from the factory. There's nothing wrong with the engine. Has about 190K.

The 90 is a mystery as I've never tried to start it. It's one Chrysler key to fit all. It's really straight but no paper, and 242K on the clock. It's my transmission/case/doors/windshield etc. Also has the late model cooling system with recovery bottle.

I'm sure there's someone reading that knows what I'm doing is wrong, and why, so I sure hope you'll share.


The 89 is T-boned on the drvers side. That kick panel is smashed in good. Wiring down there is trashed. Dash is even crushed a good bit.

It has a line at either end of the fuel rail, the pressure bottle cooling system, and and a mass of wiring surrounding a relay of some sort on the passenger fender.

The 90 has both lines up front on the fuel rail, a relay box like my 96, and some large electrical box against the fender on the drivers side.

Here's what I need to know.

Which one should I pull the harness/cluster/etc out of?

Will the 89 injectors and pump work for the 90 injection system?

Will the 90 system have the key cycle diagnostic check?

I have a lot more questions, some I'm sure I'll find out answers to as they come, but any help is appreciated. I know I'm going to a lot of trouble but it's all paid off, and it was all cheap enough, the titled body was free.

The only thing I can offer is that I've seen on a great number of threads that the engine bay on 84-86 models is different from those of 87-01s; to fit a 4.0 into an 84-86, either the firewall or the radiator mounting (maybe both? don't recall) needs modification (or front clip splicing).

Good luck.

A bolt in swap would be a 3.4L V6 out of a camaro. A SBC would be an easier swap then a 4.0.

You need to massage the firewall and do some radiator support work to make an 84-86 fit a 4.0. From what I've heard it's not too bad.

Curious why you don't just swap everything from the '90 onto the '86? The '90 sounds like it is actually a '91 with the OBD I engine management system, maybe it was a really late '90 build or you have the year wrong (would be easy to do with no title if you never checked the VIN)? Everything you've said about it points to it being a 91-95 vehicle. The mystery box on the driver fender is the ECU, the relay box on the passenger side, the cooling system, the 1-key... you name it, it all describes a 91-95.

What I would personally do: Get the '90/91 running, drive it around the yard a bit, make sure it works properly. Then gut the 86 completely, handle all the rust or anything else it has wrong with it, bedliner all the floors, let the bedliner cure, fix the firewall and rad support to make the 4.0 fit (use the radiator out of the 89 to check fitment while keeping the '90/91 in one piece), once everything is ready to roll, swap everything from the '90/91 onto it and call it a day.

The other thing you can do is (if you have the bill of sale, or proof you have had it for x years) run the VIN to make sure it isn't stolen, then either turn it in or file for a replacement title. Usually there is some way to get a replacement title, it might cost money or be a pain but then you can just leave the vehicle 100% intact.

Well, it looks straight, the 90, but it's been cobbed. The injectors are pulled, water pump missing, and unfortunately I have no extra starter handy. I'd gladly rebuild the core I have that came out, but I think the solenoid is crimped together and the motor is non user friendly. I drove the 89 in before it came apart, and with less miles, it just seems like the better donor.

From the transmission on is the leap of faith. I can see the differences in the engine bay, at least a few mounting locations. I've decided to retain the 86's axles until everything else is together.

While the drivetrain is out I can clean up and paint the engine compartment. I'm glad I know to look for differences in between so I can beat-then-paint. As the doors have to come off, the seats out, and wiring strung, I can put my body color on the door jambs and the pillars easier. Want to do a color change on it to metallic silver. I think the red interior will jive well enough. Being tall I like the AMC manual seats.

Also, it already has the 89 clip hung on it. I noticed the hood is a little shorter on an 86, it has a half inch gap at the header across the front. The latch is also single instead of tandem. I do see some things thus far that may have to be drilled and even located. I'm equipped to do light welding.

The 90 is the way to go looks like. I never cared much for GM V6s, plus I'd have to go buy all that junk or a hammered kid rod for a donor. I like the 4.0 and AW4 much better, and it's already there.

By the way, there's a real straight 84 down the road that's set up for SBC and has paper. It's on 22s, he wants $400 for the wheels and they come with the truck. I'm trying to get someone interested in the wheels so I can get the truck.

Thank you for all the input.