Previous discussion, 3/16" copper. Fittings like original may be hard to find. Alternative fittings used in new kits.

https://www.stovebolt.com/ubbthreads/ubbthreads.php/topics/1366084/1.html

Pictures from Chevytalk and 1939 Chevy manual.
Attachments
Oil Line 01.jpg (62.67 KB, 186 downloads)
Oil Line 02.jpg (32.39 KB, 186 downloads)
Oil Line 03.jpg (83.39 KB, 185 downloads)

Last edited by buoymaker; 05/15/2022 5:38 AM.

"Adding CFM to a truck will only help at engine speeds you don't want to use."
"I found there was nothing to gain beyond 400 CFM."