If you can't fabricate 1/2" steel lines and don't want to use 1/2" copper, you could use 1/2" PEX tubing, easy to work with, inexpensive, won't collapse under vacuum.
1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy
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