5-speed corncob cluster. There's a good bit of extra weight in big cogs and in that extra (6-speed) cog. I still have some good useable SunTour 5-speed aluminum freewheels but guess what - they only weigh a tiny bit less than a comparable size steel freewheel.

In the 1970's I weighed less than 130 lbs, so I could get away with lighter rims and tires, too.