You can put a 7spd freewheel on it and a triple in front. No need to cold set but you may need to manually spread the dropouts a bit to mount the wheel. You may also have to use a longer rear axle + spacer. If you simply want a wider range, the Rally should handle a 6spd with more teeth and you can also mount a modern compact crank such as

http://cgi.ebay.com/Campagnolo-Veloc...item2a067dbaf2