I am trying to sort out multiple troubles with my cluster in my 91 tb42 I bought a cluster off a 92 model carby and it doesn't plug up so rather than cut a patch lead to suit I am trying to fix my old one

my tacho I got working today (loose wire at coil)

oil pressure is working (didnt need to touch) got a pressure reg a year ago

fuel guage only half working (halfway is empty) 72litre belly tank

volt metre not working where does its remote wire to (I have dual batteries could be a removed wire or is there a fuse or relay for it)

my speedo I am sure is wrong (out by 10-15 kph)

Any help would be great cause so far none of the problems have been in the cluster itself