Those look like they could be fabricated by a first year high school machinist student, (back when they actually had those kinds of classes) but since they were discontinued by GMC, I wouldn't waste much time worrying about them. They look like the idea was to direct coolant toward the exhaust valve area of the combustion chamber.
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!