I have a line on a 1979 carbed version with the engine and transmission already out. I own a 1987 that runs and shifts great, but the body is rusty. Both lower corners of the windshield frame and across the top are gone, rust on the doors and behind the rear wheels. Interior trash, brakes junk, steering rack junk, upper shock mounts toast....the list goes on
The 1979 body is in MUCH MUCH better condition than mine. Engine was pulled due to various problems and owner wanted to do a full rebuild, just never got around to it.
My question is what all is involved swapping my 87 engine and gearbox into the 79?
Being that I have a running and kinda driving complete 1987 I imagine I have everything I need.
I'm thinking differences are fuel tank, electric fuel pump and lines to fuel rail and return back to tank. Ignition parts, box in passenger compartment behind seat, everything else on engine or in engine compartment? Is anything under the dash different, will I need to swap the entire wiring harness?
What else am I not thinking of? Is this worth doing?
I did a fuel injection conversion on my '79 and it was not that difficult. You have it made because you already have all of the parts. The fuel injection harness is separate from the rest of the wiring harness. You should get the '79-81 wiring diagram book as it has both the '79 carb version wiring harness diagrams as well as the fuel injection wiring of the '80-81s. That way you can compare them to figure out how to pull power for the various fuel injection unique parts. MWB sells it.
There are some minor problems that you will need to solve. One, how to mount the fuel pump as there are no threaded holes in the location where the fuel injected models have them. Two, the bracket with the spare tire hold down bolt is different on the carb versions, so if you plan to put the computer behind the spare tire, you will need to decide how to do it. The spare tire on the carb versions is put in with the outside facing the firewall, whereas the fuel injected cars have the outside of the tire facing forward. I ended up taking the computer off of its frame and mounting it directly to the firewall, that way it still fit under the bracket and I could still put the spare tire in. You will have to cut the hole in the firewall for the harness.
One cool thing is that the bracket that holds the fuel filter for the fuel injection mounts right to the same bolts next to the fuel filler neck that hold the blower fan for the carburetor on the '79. The bracket that holes the air flow meter is almost a direct bolt on to the same angled bracket that supports the fan motor. Unfortunately, the mounting bolts are shorter than they are on the fuel injected versions. I cut off the bolts, drilled them out and then epoxied longer ones up through the holes to attach the AFM. The air cleaner also attaches to one bolt near the fuel filter but I had to drill and tap a hole for the other attachment point on that angled firewall bracket.
You will have to figure how to mount the fuel lines to the body of the car. There are no punch outs for the little plastic brackets that hold the supply and return fuel lines in the '87. Changing the fuel tank is pretty easy. One of the holding straps for the fuel tank of the '87 has an extra threaded bracket for attaching the fuel pump protection panel so be sure to swap that over. If you are able to mount the fuel pump on the '79 in exactly the same spot as the '87, then that panel will also attach to the fuel pump bracket.
If you want to add the blower fan in the trunk, there are a couple of snags here. First, the antenna is on the left side, instead of on the right, so it takes up space where the blower motor would normally sit. Plus, the mounting brackets that Fiat added for this blower motor are not there so you will need to come up with another way to hang the motor. I ended up angling the motor so it would clear the antenna, and then I drilled a hole behind the left light cluster and epoxied a nut there to add another attachment point for the motor. I can take some pictures of how I did these mods if you want. Make sure to take the access panel from the '87 as it has the blower channel built into it.
You mentioned changing the entire wiring harness. The fuse panel and wiring harness for the '87 is more modern and way different than the '79. I think it is much better, and it has all of the circuits and relays needed for the fuel injection system. But, all of the console switches and connections are different, the headlight switch is different, the wiper/turn signal switch connections are different. So if you want to swap in the '87 wiring harness, be prepared to change over a lot of other electrical pieces. There will be wiring for things that the '79 does not have, like courtesy lights in the doors, power windows, among others.
I realize that this was a bit long winded, but it is definitely doable, it will just take a little ingenuity.