Not to argue, but with updated 6-speed gearing on the back, that SIS derailleur will work perfectly. Original derailleurs, like an older Simplex, will need a huge amount of travel in the shift levers to operate fully across 6 gears. At least that's been my experience. Of course I'm a "handsome is as handsome does" sort of person. Be careful with the position of the skewer on the non-drive side. It doesn't seem to be on there by much. Looks like a fun ride.