Some previous owner of my 620 switched out the Helicomatic hubs for Shimano hubs, so the 27" wheels are pretty acceptable. I would eventually like to switch them out for 700c so I can get some decent tires wider than 27x1 1/2 on there and switch over to a cassette in the back in order to go to 9 speeds from 7. But this means fiddling with the cantis and maybe spreading the rear dropouts and whatnot, so it's probably more of a long-term project.