Under dash wiring from donor vehicle

[fastlane]

I bought a 03 express van for the LQ4.i was working on removing the wire harness this afternoon with my son (7, took 3 times as long but we had a good time!) I did not cut anything accept the headlights (corrosion) I disconnected the wires from the CPU and took apart the fuse box. What do I need under the dash? I'm assuming the OBD port. What about the ignition?

It's not in great shape, it's got a spot that rubbed against the motor and quite a few areas right near the CPU have rubbed through, I'm really considering a new standalone harness, but my budget would like performance parts! Performance parts that would be useless if it doesn't run! 😂