It's a front axle.... ;) BTW - what has lead you to believe it is not original?

That looks like a solid state relay.too posh for me.

R380 stumpy box exists to allow as a direct fitment (mostly) for an LT-77. This was done to allow warranty claims on LT-77's after production stopped. 1.6 transfer box was usually only on military 110's and with a Tdi will give way too short...

This isn't the same as yours I know but given they share similar heritage, there may be a few shared design cues (unless it was all made up with whatever was in the shop). My Tithonus TUM FFR (Defender 110) came with a 200TDi Disco engine...

Then do a Damp Recce

This^^^ LEDs are very sensitive fluctuations and require good cabling and connections. On mine I have added an extra eart so in the rear corner all of the earths go to the earth screw which has been replaced with a bolt and then on the underside...

I'm going to take a look at the bulkhead fixing. Maybe a couple of new plastic vents and some self tappers / rivnuts might work. Guess it might also have a further knock on effect to the heater ducting etc.

Check all your earths first and magic might happen!

Wild idea and no idea if it's doable, could you get a replacement 3D printed?