Isn't that tube only used on spray-oiler Babbit connecting rod engines? Some of the early 235's had a tube from the rear camshaft bearing oil passage under the pushrod cover to the oil connector of the rocker arm shafts. That tube can be replaced with a piece of 3/16" steel or copper/nickel brake line, since it doesn't come into contact with the coolant. The spray oilers need to use copper tubing to avoid rust-out. Most of the resto-ripoff suppliers have a kit with tubing and fittings to replace the spray oiler oil tube.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!