while I've never replaced a wiring loom becuase it's was an on it's way out - I am currently rebodying my March '77 120Y (B210) four door sedan into a spare July '74 120Y (B210)4 door shell

under the dashboard you will find 2 rectangular plugs - they hook up to the engine bay wiring undo these and the three bolts near the windscreen, the 2 that hold up the dashboard, and the 2 that hold the steering column up

and not to forget your speedo cable

and the whole dashboard is out

use a 1/4 drive set... otherwise you won't get anywhere...

apart from dashboard wiring and engine bay wiring loom I've switched over wiring looms...

those square plugs aren't easy though...

I may dremel the locking clips off if they don't unlock...