Vacuum question!

The cam is V 9215 Part # 2-000-5. I cant find it at comp cams page so i guess they dont make it anymore?

How much vacuum is, so to say, wanted in a streetable car? Im not so good at this as i only have begun to understand engine buildning, but im trying to learn!
How much agressive cam would be wise to go for ? How would the gain look like? Would there be any big difference ? :)

My friend who helped me measure told me that 15 ipm is more than a stock 340 had in vac. ! Is the vacuum mostly becuase of the cam or is it more to that the engine is stroked and has small intake channels for the displacement ?