Look for an oil passage in the cylinder head that would be used to provide lubrication to the rocker arm shaft. There might be a tube that joins a port or an oil gallery in the cylinder head to the shaft. I haven't built enough GMC engines to have the oil circuits memorized.
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
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