The engine was fully built in the winter of 2013. A bad turbo install in 2016 resulted in building the bottom end again this year.I don't think I'd run a stock motor with over 450 whp.
I usually cut them off at 450whp stock as well. But even at that number they're 11.4cars at full weight and less with less weight. Get your launch perfected some more and you'll keep seeing improvement.