Building an 89 YJ with a 94HO 4.0l.(Project is with my 15 and 12 year old boys) I was just looking to find out if I should grab a complete interior harness out of a fuel injected or if the harness in my 89 is compatible with just minor changes. I have the engine harness and ecu and fuel tank from the 4.0l but I wasn't sure if I would need the wiring to the fuel tank from a newer one. Hopefully I can get a build thread started soon.
Ive done this exact swap (but that was 6 years ago so its a little foggy). You do not need the interior harness at from the EFI at all. You Just need to match up the wires in the bulkhead connector. (The connector is in 2 pieces, half is for the engine (PCM) other is for lights/fans etc.) The one for the lights and everything are the same, plug and play. The engine one you will need to move a few wires around and then plug it in.
I still have all the wiring diagrams somewhere that I can get to you.
As for the wiring to the fuel tank i just ran a new wire throught a relay back to the PCM.