All Chevy engines I'm aware of have distributors that turn clockwise when viewed from the top. Turning the housing CCW advances the timing, CW retards it. The vacuum advance pulls the breaker plate on V-8's, or the whole housing on stovebolts opposite the direction of rotation, causing the spark to happen sooner under high vacuum for better fuel economy.
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!