My only logic based guess as to why an ISO taper on a Japanese part is this; ISO was the dominant taper in track racing so Sugino followed suit. They never imagined us using the parts in the way we do so ... this is what we end up with. Mfg's that dominated the track market in the 80's & 90's were Campy, Suntour Superbe Pro (my favorite), and Shimano (10pitchDA-octalink after?) to a lesser degree I think (someone pipe up if I'm off on this please, I am assuming to a degree) In order to stay competitive with the Q-factor (space between the L & R crank arms when mounted) of the other mfg's. So, Sugino stuck with the standard which is ISO. Oddly the UCI is based in Switzerland and so is ISO ...hmmm. Anyway, I'm wayyyy to OCD about matching parts to their parent & sibling components to be bothed trying to figure out how to make something not meant for it work; but that's not to say other can't do that, as I have seen it done for years. When I bought my first Track frame in 2003 it came woth Suntour Superbe pro track 170's on a Shimano Un53 BB, I ran a miche BB for a long time because it was ISO and with no Drive side BB cup flange I could migrate the BB slightly to correct my chainline. With in a year a rare stash of Suntour track 107mm BB's showed up on EAI and I bought it for 100 bucks; it is and has been perfect. I would save up for the sugino BB if you can swing it, it will last for a long time if you take care of it.