I went basically from
http://www.bmwe34.net/E34main/Upgrade/More_light.htm . Main difference, you don't need to change o-rings. Also, if you've got a flat file, it'll fit nicely between the contacts and the bits you need to file down. You don't have to remove all the ridges, just far enough back to let the connector fit on.
In case the page dies, I sum up:
Take the bulb and put it base-down, length of bulb facing away from you so you can see the tabs facing you. The center tab needs to have about 2mm of material removed until it's skinny like the 9006 equivalent tab. 9005 bulbs are uncapped.
