That looks very much like something that would have been connected direct to the battery? By the diameter of the orange +ve cable and the black -ve cable (and the ring terminals) it looks like the setup was design to carry way more load than the connector behind the dash would ever be able to safely provide. The dash connector is good for up to 7.5A, but even then that's pushing it. 5A would be a safer bet.

I think you would be best connecting that lot up directly to the battery if you're going to use it on the Z. It would be the safest option. Mind you what does it all do??

Just out of interest, what is the rating of the fuse in the holder on the orange wire?

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