I am breaking my project down into "modules" i,.e suspension, body, motor/transmission etc and one big aspect is more or less restoring/upgrading the wire loom i.e. electrics.
I presume it was done according to some British standard.
I actually have 2 looms from the two cars I bought (`72 European and `76 Federal) plus a guy gave my a European MKIV loom of unknown model year so I have lots to check.
However, should I need to replace a wire/cable I would want to get as close to original as possible (or even slightly larger...)
I did several searches but all I could find was the European standard: https://en.wikipedia.org/wiki/IEC_60228
But I am not sure what standard was used on our cars so no clue what the equivalents are. (I do have the Lucas chart for the standard of what colors are used for what on a typical loom)
Just buying a new loom doesn`t make sense because the car will have multiple upgrades such as relays for headlights, upgraded heater, possibly subtle DLRs/fog lights etc... Engine mgmt will also be nonstandard...
Cheers and have a great day!