I just put a modern, 7 speed, 13-28, ramped IRD freewheel on my old Fuji Allegro commuter. Works beautifully with my downtube friction shifters, although I had to tighten the levers up a touch. For anyone contemplating such a move, upgrade the chain too. The IRD freewheel did not play well with my old chain, which was working OK with the Suntour 6 speed freewheel. A modern SRAM PC-58 (Jenson has a nice price on this chain) does play well with the IRD freewheel. The upgrade in shifting was like moving from a crusty, old dumptruck to a modern, Honda civic. Smoooooth, even under load.