You will need to "level" the lathe, regardless of the surface it rests on. When we speak of leveling a lathe, we are actually speaking of getting the two ends of the lathe co-planar so that there is no twist in the bed. A precision level will read the same at the headstock and tailstock ends, even if the lathe itself is not level with respect to the surface it sits on. So yes, you need to "level" the lathe.