Not sure what you mean by "adapt" then?

Did you look at the picture of tube nuts I provided in an earlier post, and understand that they come with different thread sizes?
Can you simply use the proper tube nut for the MC and residual valves with whichever size line you need (sounds like 1/4")?

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-