[tirwin]

Here is a link to the electrical diagrams. 78 should be the same for your 81 I believe.

Pelican Parts - Porsche 911 Parts Listings & Diagrams

Good resource on European wiring:

http://www.thesamba.com/vw/archives/info/wiring/Understanding_Euro_Wiring_Diagrams_Motor_Magazine_ April_2003.pdf