[papajam]

Sniady and rcess bring up a good point about safety and possible US regulations stating that headlights not be triggered by the ignition switch. While it may be a US reg today, it wasn't from at least '71 thru '84. The three early '70s US spec Bavarias and an '84 Subaru I owned had ignition triggered headlights (the 'Brews parking lights stayed on though - a lot of good THAT did to save the battery!).
To wire your car for triggered headlights, all you need is a Bosch or Hella 15A relay or equivelent. The fusebox in the diagram is a '69 - '74 US spec 105/115 series. Here's what to do;

Wire #1. Remove the red 12ga wire (that feeds the headlight switch) from the top of fuse #3 and connect it to terminal #87 on the relay.

Wire #2. Run a jumper wire (16 ga will do) from the top of fuse #6 (or any switched power source) to term #86 on the relay.

Wire #3. Use a 12ga wire to jump from where wire #1 used to be on the fusebox to term #30 on the relay.

Wire #4. Ground the relay (term #85).

That's all there is to it. Keep in mind though that a 15 amp relay may be undersized if you have lights that will melt the bumpers off the car in front. If that's the case, then you need to relay the headlights as well. Diagrams to relay the headlights or to add a buzzer will be posted if anyone needs 'em.