All I looked at was Philips H4. I think they come in very, very few bases. They are magnetic. So the light source is singular and a "shade" on a magnetic solenoid (is there any other?) moved out the way to provide the high beam. My concern is the shade. The stock one may have to come out making for a little more work.

__________________
1991 560 SEL / 185k miles
1992 750il / 17k miles - project car