JIS headset question
 

I'm overhauling a 1973 Schwinn World Voyageur.
The headset cups read 30.0 on a digital caliper; the fork crown race is 26.4.
Most headsets I've looked at ship with 27.0 races combined with 30.0 cups.
Can I substitute a 26.4 crown race from within the same manufacturer family?

Say, this:
http://www.benscycle.net/index.php?m...oducts_id=8193

with this?
http://www.niagaracycle.com/product_...7e16bd6378121f

Maybe. Are the ball sizes the same for each race? How is the dimensioning of the race at it's base/seal fitting? There's a lot of class B fits out there but without actually trial fitting i wouldn't want to make any promises. Andy.