Originally Posted by
Road Fan
I concur completely, with the possible addition that the wider Megaranges, 13-34 7-speed, give a highly usable spread in the first 6 positions. With a Duopar, the difficult-seeming shift from the 24T in position 6 to the 34 T in position 7 is a piece of cake. It's not a piece of cake with a Shimano 600 long cage. With that cluster and Duopar derailleur your 52-40 crankset does not have to be changed.
I'm using one of those Megarange 7 speed freewheels on an '88 Schwinn LeTour. I put a Shimano XT rear der.(not sure what vintage, it's silver colored) and it handles the 24-34 shift effortlessly.