Vintage 5-7sp freewheels. Modern 7-sp freewheels in silver look vintage correct and work identically, but give much smoother shifting, so why put up with needlessly clunky shifting and fewer gears?
Thinking of 1970's road bikes here, I'd add galvanized spokes, hookless rims, steel rims, 27" wheels, cellotape, stem shifters, steel drop bars, seat pillars, and low end stuff in general - it's not that hard to find period-correct parts or visually identical modern equivalents that are much nicer, so why put up with a sub-par vintage experience?