Usually brake hardware will accept a couple different size lines if you use the appropriate tube nut.
There are a number of different thread sizes to choose from to match your hardware, and often your choice of line size, here is a handy picture with most (not quite all) of them. 7/16"-20 for both 3/16" and 1/4" aren't shown, at the time I couldn't find them in stainless and haven't looked for them lately.
https://picasaweb.google.com/lh/photo/NRKuDQEmlKs1crsrTKN7ENMTjNZETYmyPJy0liipFm0?feat=directlink
It's been a little while now but I imported and sold CuNi line and sourced stainless tube nuts, now the line is easy to get at the auto parts store.
The stainless tube nuts I was getting in large quantity form BrakeQuip as well as assortment packages from Summit Racing.
http://www.brakequip.com/tubenuts.html
http://www.summitracing.com/search?keyword=stainless%20tube%20nut&dds=1

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-