My brothers going to be doing most of the wiring, but so far (our is an E30/M20) we've used the engine loom & the lucas loom supplied by Marlin.
Took the outer plastic off the engine loom to re-route a few bits and replace the alternator -> starter -> battery cabling with newer thicker stuff.
Chopped the engine to car loom plug off the donor loom and when from there using technical drawings I found on
www.e30zone.co.uk -> probably not much good for your donor unfortunately. Perhaps someone at
http://forum.evotechnik.net/ could help.
Robin used the car loom from the donor keeping the fuse box, but stipped out all the bits he didnt need. I'm starting to think we should have done it that way too.