Check out Sheldon Brown's site for his charts on spindle sizes per brand of cranks...
Spindle sizes can range from something like 101mm to 130mm or even longer.... it all depends on what crank you are using, with the BB as different brand have different chainring offsets. Taper standards will need to be considered too (JIS or ISO and maybe some proprietary tapers from smaller or obscure brands). I think most or all Campy cranks are ISO.

Chombi