Are all of them adjustable, or only the ones used on mopar performance distributors? I kind of suspect (but could be wrong!) that only the later and performance ones were adjustable. That old 273 distributor may be a cast iron unit as well.
They are all adjustable. The "normal" ones use the hex key, while the cast iron Prestolite distributor used washers. I really hate to say all anymore, I guess almost all...