AKA "Reading Sheldon Brown makes me even more confused"
He mentions in his freewheel article that a "narrow" 6-speed freewheel will fit in a 70's 10-speed frame because of the chainstay spacing. However, he never says what "narrow" is.
Does this mean I can screw on, say, a Megarange freewheel onto my bike wheel without redishing it? With redishing but no cold setting the chainstay? Or is this narrow freewheel some obscure boutique part made by monks in the 1960's that only fits French threading?