This is an old cylinder I have, it looks clean enough, but even with a honing and new seals did not work. I'd simply buy a new one.
Regarding the wiring loom. I re-wired my own car using coloured wires. After tagging each end and taking lots of photos, I took out the complete with fusebox attached. Laid it on the floor and fitted coloured wiring,each circuit at a time.I followed the colour coding as used on modern Fiats. I left each wire maybe a foot longer, which gave a bit of freedom when refitting.
I got a local auto tech to rewire the 'other' B20 I am working on. What he did was clever, he used coloured wiring, but covered each wire with 'shrink' black coloured tubing. This gave the impression that the loomwas original, yet also provided a little bit of colour to be able to connect properly.