Iron/iron combos don't change much at all.
But the point is, on a solid cam, you don't want the operating lash at zero. Keep in mind that I said operating lash, because there are some special conditions (all aluminum stuff with tight lash cams, or hydraulic roller cams running solid roller lifters
, etc.) where you have to set the cold lash at zero or near zero. When you get to that point, sometimes you have to preheat the engine before firing.