The drilled center head bolt was only used when certain block and cylinder head mismatched years of production was used together. As long as there's at least a seep of oil coming from the holes in the top of the rocker arms at idle speed, the rockers will be lubed sufficiently. At cruise speed, the flow will be considerably higher.
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!