you might want to ask HellCreek to be sure, but I'd hesitate making that much of a comparison between brand new lift leafpacks and the old factory leafs. the number of leafs does not necessarily directly correlate to an overall stiffer leafpack (thinner/thicker leafs, softer/stronger steels, etc).
Yes, the factory metric tonnes had a 4+1 configuration while stock factory leafs had 3+1.