I converted a Trek 614 frame from 27" to 700 and found that standard (long) reach shimano brakes where just a bit too short. I filed the adjustment slots about 1/8" longer and they now work fine. An old Raleigh Supercourse made the change without any brake alterations at all. You won't know whether cantis or V-brakes will work until you test fit them. Just make sure the vendor has a return policy before you order, then experiment until you find something that works.