Here's what I was working with, and this may explain why I decided to do certain things. I have a US spec 91T, and am putting in a 95 or 96 JSpec gen3 engine. I am using the 91 style taillights, and 91T gauge cluster.
1. Main wiring harness for Gen3 (left), and Gen 2 (right) from rear trunk to front kick panel.
2. Starting at the rear of the harness (and car).
Plug 1 is exactly the same. It's for the antenna.
3. These are not the same. They are male for the gen3 and female for the gen2 as well as differnt wire combo. Check out the gen3 taillight wiring page for info on how to use 91 lights with the gen3 harness. The plugs in this picture are for the passenger side taillight.
4. Gen2 alarm connection for rear trunk which I bypassed long ago. My Gen3 harness does not have an equivelant in this section.
5. These are all exactly the same. the opaquish one is for the license plate light bulbs, the red wire with grey plug one is for the trunk open/close sensor (not 100% sure on that), and the loop is a ground strap.
6. Here, the gen3 has a connection, and the gen2 does not. This is the reverse lights, which the gen2 has already included with the taillight plugs.
7. Movind forward a little.
Another plug where one is male, and the other the exact female counterpart. Different wires in the back too. These are the drivers taillight plugs.
8. Close enough, should plug in. These are for the trunk dome light.
9. A little different, but they go to different ECU's.
10. Basically the same here for these. Gen3 in this pic, and gen2 in the one below.
On my Gen 2 I had bypassed one of the relays, that's why this only has one plug.
11. Same.
12. Engine hood temp sensor. Same.
13. Moving forward a little. We are now inside the cabin, behind the drivers seat and carpet.
This plug has a different wire layout, but don't worry, just plug it in.
14. This is a ground strap that connects in the area above the subwoofer.
15. This section here does not exist on the gen2. It's for a noise filter box that came with my gen3 clip. You most likely do not need it if you don't have the filter.
Gen2 pictured here, one goes to the drivers speaker.
Gen3 has a different connection. Do the gen3's have different side speakers?
16. Top of this branched off section.
Same. The top is for the drivers taillight, and the bottom is for the rear window defroster.
17. Last part. These go to the kick panel at the drivers left foot. This section has 4 white connectors.
Plug 1 has just one wire.
Plug 1. They are female and male though, so the heads need to be switched over.
Plug 1. Here's the gen3 opened up.
Plug 1. Doh, gotta switch those around. I ended up just cutting the wire, switching heads, and soldering.
Plug 2 here looks very close. Just a few different wires. In the end it didn't matter, it worked fine.
Plug 2. Not exactly the same, but close. It worked fine, no splicing :)
Plug 2.
Plug 2.
Plug 3.
Plug 3. Not the same number of wires, and locations, but plugs in and works fine with no splicing. This plug does have one thing that you'll want to do to it if you are using the gen2 gauge cluster, and that is to cut the green wire with white stripe. If you don't do this, everytime you step on the brakes, the airbag light will come on. Cutting it has no ill effect on the car. The gen3 airbag either must not have a diagnostic capability, uses another pin, or indicates a problem somewhere else.
Plug 4. Not the same exact colors or numbers of wires.
Plug 4.
Plug 4.
That's it. May look difficult, but it's very easy to put in, and requires only one splice of that #1 kickpanel plug to get your car running. The rest is just taillights (unless you have 94 style already), drivers main speaker, and door sensor.