Many muscle car rebuilders use the Cu-Ni tubing since much easier to bend by hand without kinking. You can make bubble-flares with a common "double-flare" tool. See youtube's. Many do since they have that tool and the "correct" bubble-flare tool is ~$250.

If you can't bubble-flare, you could use an inv flare in-line coupler. I have bought those in bubble-packs at Autozone. I have used inv flares on newer U.S. metric tubing (6 mm, forgot). Haven't touched my M-B brake tubes and don't know what size that tubing is. Of course, better to avoid adding couplers since more places to leak.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans