Donny,
I am in the process of doing the same thing. The car I am currently working on came with no clutch hard line at all. I was able to source the metric tube nut that goes into the clutch master. I am using .25" copper nickel tubing for the section to the engine bay. I test fitted the tubing into the nut and it fits okay and is a little on the snug side as your measurements suggest. Here is my test setup.