Originally Posted by
Hondo6
Pretty sure that a 27.0mm fork crown diameter means it's JIS. If memory serves, those IDs for the upper and lower headtube ID are also consistent with a JIS headset.
Yes, the dimensions given for the VO unit are JIS. A JIS frame/fork can be milled to accept an ISO headset, if it comes to that.
The VO headset is nice, but it's relatively tall.
Headsets with aluminum cups are taller than those with steel cups, as the aluminum parts need to be thicker than steel parts. Most Tange headsets are available in both JIS and ISO dimensions, and many decent steel models are available. Other companies may also have offerings in a variety of stack heights.