Not sure if this has been posted before, or if it is 100% accurate but I found this while surfing. It is a really well done write up in two sections.
A)E30 Headlight Wiring instructions Converting sealed beam to ellipsoid/european style headlight systems using single filament bulbs
B) E30 fog light wiring instructions, conversions allowing for independent fog light operation in sealed beam and ellipsoid style headlight systems
both are in PDF format.
here are the links
A)E30 headlight wiring instructions:
B)Fog Light wiring instructions:
Hope this helps, have not had a chance to fully read it yet, so if anyone can verify its accuracy please do.