rebuilding my carburetor, and I'm wondering where those gaskets go to.

By the way, what exactly is the gold hex thing, and what is its purpose?

I already replaced all of the gaskets in the float bowl, btw.

This set is also from Victoria British, if that helps.

Carburetor kits typically cover more than one carb model. Take one apart at a time on a large clean surface like an exploded veiw. As you lay them out, match the new parts and take notes if you need to. Clean each part individually with carb cleaner, rinse with water and spray with WD40. Use the other carb for reference for reassembly. MSA sells a book on SUs. I don't have it but it probably could save you some greef.