The naturally aspirated LS7 is the same motor we know and love from the C6 Z06 and it is rated at 505 horsepower at the crank. Redline Motorsports put a bone stock Z28 on the dyno and showed 455 to the wheels.
Now, this is a Dynomite dynamometer which reads higher than a Dynojet. Stock C6 Z06's put out roughly ~440 whp and that will be the range for the Z28 as well. The car is spot on exactly where it should be.