I'd guess the clutch is 1/4" line.
Brake lines may be 5/16", but if not they'll be 1/4".

If you want easy to bend and flare lines that last near forever try some nickel copper, NAPA has this available, or you can find it cheaper on ebay.
http://agscompany.com/product-category/brake-fuel-transmission-lines/nicopp/coiled-tubing-nicopp/

•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-