Should the hose off the brake booster suck air or blow air?

I am putting power brakes on a 68 firebird that originally had manual brakes. Disc front and drum rear. I also need to know the following... should the master cylinder sit in position level or at an upward angle? It also had originally 2 types of valves running from the master cylinder... A rectangular one and a round one... seeing as I'm going to power brakes... Do I really need the round one hooked up anymore? Thank You