Adding a thread here for a way to log progress and hopefully help others in future.
My 91 Defender 200TDI (which I now have learned contains a Disco engine) is failing to start after I've replaced the steering shaft and radiator - doing the...
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...