AMG S63 motor world's most powerful naturally aspirated V8

We posted yesterday on a spy shot of the AMG S63 and talked a bit about the fact that it was nice to see Mercedes returning to a high-horsepower naturally aspirated powerplant after employing supercharging in many of its recent motors. Well, AMG is actually claiming that its hand built 6.3L V8 that cranks out 510 horsepower is the world's most powerful naturally aspirated V8. Unfortunately no one here at Autoblog has a Guinness Book of World Records handy. Can anyone either corroborate or contradict AMG's claim of building the most bullish V8 on the block?