Paul's right, anything prior to the 4-fuse models starting around 79 (co-incides with the BTZ ignition, but is not strictly related as the ignition has its own loom) has only a few wires running down the spine of the frame. All the distribution is done in the headlight, hence the spaghetti junction there. Bosch or ND switchgear makes little difference as far as I know. The difference is the 4-fuse setup, as feed has to go up the front, back to the fuses, then multiple circuits have to go up the front again. Overall a better setup to have the functions split onto seperate fuses though (IMHO).
I had little experience of the early loom until I did Eddie's 1200, it was a mess of a bike as a starting point and I'd seen photos and disparaging comments about the headlight mess over the years so figured I would just replace it all and make it like a later bike. When you actually analyse what's going on inside the headlight it's not a bad system - all the connectors are in a more or less waterproof housing, and the loom is small. The big chocolate blocks are just distributors for various functions like switched 12v, lights, earth, etc. Where it falls down is lack of space if not packed in properly and heat if the headlight is used all the time (as is required in many places). Having to work out what plug goes where is inconvenient if removing instruments or switchgear, but rarely required. The worst part of it is there is no dedicated earth wire, I installed one back to the earth point near the coils, recommended.
Getting back on topic, Wolfgang certainly had repro pre-79 looms a few years back, contact him and see. There is a bit in them, and many people do not do proper crimp joints, so better to buy pre-made if you can. Reports from people who've used them are that they are well made and easy to install (experience on triples, but likely same for twins).
