'66 273 BBD Carb

Dana67Dart said
Ford used a plactic cap that snapped on the outside of the screw to prevent more than a few degrees of rotation.

Easy to remove.

I think I even saw a screw like on the bbd on a motorcraft 2 or 4 bbl at one point

Even my lawnmower has a plastic cap. :)
Covers are common on motorcycles. A sheet metal screw pops them right out.

I may punt on this and use this as an opportunity to get a 4 bbl. I love the original 66 small-bore air cleaner though.