Have a look at my thread here about rebuilding mine after an engine fire
LINK. and my specific thread on the under bonnet fuse box here:
LINK. Although it is '89 reg it is running 300tdi wiring looms throughout. The engine bay fuse box you are referring to is the main fused link between the battery and the rest of the vehicle wiring. It does from the back of the starter solenoid (same as the battery positive cable) up to the fuse box with the four large fuses mounted on the passenger footwell. if you have a loom form autosparks they include a new but non original fuse box for this so you only need to manufacture the half from the solenoid to the box. I wanted to keep things original so I bought a second hand fuse box from an auto jumble, salvaged the main loom connector from my donor bulkhead and then replace the autosparks spaded connectors with the ones here:
link