The 27mm crown race seat on the fork is Japanese Industrial Standard (JIS). The 26.4mm crown race seat is ISO standard. Crown races come in both sizes and your headset vendor should have a 27mm JIS crown race that will work with your headset. You buy the headset which comes with 26.4mm crown race + the 27mm crown race and ditch the 26.4mm race which came with the headset.

Cane Creek customer service was very helpful, gave me the part number for their 27mm crown race compatible with 40 and 100 series headsets right over the phone. Call your vendor and ask them if they have a 27mm crown race for use with your headset.

An option is to have the fork milled from 27mm to 26.4mm so that it uses an ISO crown race. My experience is that few mechanics nowadays know how to do this and few will understand what you are trying to do when you ask. Park Tool makes the milling tool so don't let anyone tell you that you don't know what you are talking about. I could only find one guy in Atlanta willing to do it, a guy in his 60's who used to build frames.

Another option is to gently file the crown race seat. It takes some time but it can be done this way if you are mechanically inclined and very patient. I did this once, using a fine file to slowly remove metal and measuring frequently with a caliper. Eventually the 26.4mm crown race was able to be pressed on.