Stunning newly released renderings show key parts of Penn Station before and after its planned $8 billion overhaul — which proponents Monday predicted will make it “America’s world transit hub.’’ Photos depict the decrepit Manhattan station’s current bulky columns on a dimly lit train platform — and then the elimination of the columns and the addition of more commuter-friendly lighting and higher ceilings in new schematics. Another series of shots shows a current run-down ticketing area