for my two '70s 531 frame 700c conversions, i used two different sizes of tektro side-pulls. on the rear of these two, i used their r559 extra long reach model, and on the front, used the r539. harris cyclery sells them individually. the r559 would have worked for the front, but it looked unnecessary. the result is a fairly elegant finish, and excellent braking, especially with the addition of kool-stop salmon pads added to the tektro holders.
