I also found I needed lower gearing to get up and over the hills of the San Francisco peninsula. I tested a 1988 Chorus with both a 7 speed 13-32 IRD freewheel and a 6 speed Shimano megarange freewheel (14-34). The 6 speed Shimano freewheel shifted better than the IRD, gave a lower lowest gear, and was about 1/3 the price. Note that rear derailleurs from the early 1980s were not as good at maintaining a small constant chain gap between the freewheel and the jockey pulley as more recent derailleurs. Thus if you set up the derailleur to clear the largest rear cog on a wide range freewheel, there will usually be a pretty large vertical gap between freewheel and derailleur pulley when you shift to the smaller cogs. As a result, you will have to overshift the derailleur to get the chain to deflect enough to hop between cogs. On a 7 speed freewheel with narrow lateral spacing between adjacent cogs, this can create problems of jumping over adjacent gears. On a 6 speed freewheel with wider lateral spacing between cogs, the shifts often work better than with the narrow spaced 7 speed freewheel. Frank Berto recommends 7 speed freewheels only for corncob gearing on 80s bikes, but 6 speed freewheels with wider lateral space between cogs when you go to high tooth counts, lower gearing, and therefore larger chain gap between freewheel cog and derailleur.