[AZKen]

Don't think it makes any meaningful difference one way or another (to the motor). The Jolly page advertisement can be a guide or not. The can, in back, has it's own "intake". GMC called their system PCV. The advent of the vented valve cover was to release "crankcase pressures" said to cause oiling issues. So engineers decided to have it vent out thru there. They added baffling inside the "breather" to prevent oil from coming out. All kinds of set ups, pre smog/post smog.
Looks like stock for your motor is non vented covers.