something like that might be very hard to pin down. given Bianchis (like everyone)habit of using the same frame for different models, Like the Formula and Formula 2 Columbus, the same run of frames could be used for years. it is possible say major switch was done in '85 for Italian buiilt bikes but there was a large quanity of sa 61cm frames from '84 those would be used until exhausted. so it would be possible to have a '85 CdI with the cables under the BB in a 55cm but on top with a 61cm. I'll see if I can tell in the catalog pics later when I get home.