360 Questions.. pardon my ignorance.

Most trucks I've seen didn't have that osac thing.
Mostly cars over about 2-3 years in the mid 70s. It was gray/black, sometimes on the air filter housing sometimes on the firewall and the VA line went from carb to it, then to the VA. Best thing to do if there is one would be to run a VAC line right from that same port in carb straight to the VA and forget that valve is even there.