In regard to machining the crown race seat to accept a 26.4 ID crown race, I was just looking at the Park tool site and their tool for this (some bike shops will have it). If you do it, you should mill the crown race seat down to 26.5mm so that it's slightly larger than the 26.4 ID crown race; the crown race can then be pressed on with the correct interference fit.
Here's a link to the tool:
http://www.parktool.com/products/det...9&item=CRC%2D1