ALL - Anyone know this? I need to clean out the threads on the reflector boss and the best way I believe is to run a dull tap into the boss. Crud in the threads there should come out just as tailings would...
Below is a sketch of the US version of headlights. Maybe that will help ID what threads you are trying to fix.
Assuming you have one of the screws you are asking about removed, it should be simple to ID its size/thread pitch.
I wouldn't use a 'dull tap'. What you want is a re-threading tap. Or find a new screw of the same size/threads and cut a groove along its length to make your own re-threading tap. The groove puts a sharp edge to scrape the old threads clean and gives the crap (in the old threads) a place to go.