That's freakin amazing on a stock block.
It would be interesting to see if a 5.3 with the different stroke, rod length/angle, and different piston tops would have faired as well?
I'm sure better than the old 5.7, but sometimes factors other than displacement affect overall power (especially on a force fed motor). Normally aspirated is usually a case of "no replacement for displacement", on a forced induction motor (depending on the platform), bigger is not always better.