any images of the battery connections main earth cable and the starter motor and alternator connections .have you checked the output voltage on the alternator main connection and then on the starter motor main connection and then the battery
on the rebuild was a discovery harness used for the engine connections utilizing the bulkhead plug etc and spliced into the original body harness or the whole vehicle TD5 harness used
before condemning the battery and alternator as steve2286 said DVM. you could have loose or broken wire's to the alternator loose or badly corrode battery connector's ,badly corroded earth connection so look for corrosion on the cable crimps...
If you are interested, I can go and measure the dimensions (although mine is a 2001 FL1 Td4, not a facelift so maybe the centre console etc is not the same, so dimensions you would need wouldn’t be exactly same?) Not rocket science tho.
they are in PNG format and rendered with MS paint so the colours do not bleed into each other unlike other formats so if you down load them and open with MS paint and zoom they should stay as is