What fitting is this?

For those people that do not want the hassle of using adapter fittings, just do what Chrysler did. Chrysler's oem brake line came with the correct 9/16-20 nut fitting on the brake line, so the adapter is not necessary. Search eBay for 9/16-20 inverted flare tube nut fitting. Of course this means you will have to make your own lines.
I made that decision long ago. I even save the nuts off lines for fiture use.