I just measured a bunch of spindles, distance across flats, 3mm from the end.
Stronglight is definitely the smallest, at less than 12.75mm for several samples
Campy world logo spindles (7 samples measured) come in around 12.80mm, with +/- .03mm of variability, a surprise.
Shimano BB's (no Dura-Ace) come in at 12.87mm on average, with over 10 samples measured.
A tenth of a millimeter difference gives about 1.5mm difference in the chainline, so a maximum of 3mm difference in chainline would occur between the smallest (Stronglight) and Largest (Shimano).
I couldn't measure taper angle, but the Superbe samples measured only 12.65mm (in addition to their reported shallower taper).
I have a Stronglight triple spindle available, if the original poster wants one, for $12 shipped.
David Snyder
Orinda, CA
USA