30 hp peak power but they are different engines and will have different area under the power curve.
A C6 LS3 with Z51 should perform very much on par with a C5 Z06. There are a lot of videos out there of these two running, the C5 Z06 usually edges it by a very slim margin if both drivers are competent. It is really a driver's race.
Here are some videos of what a C5 Z06 will do stock on the hands of a competent driver.
http://www.rangeracceleration.com/Driver_Cred.html
11.81 117.26 Bone Stock on Stock Tires.
11.55 117.69 Bone Stock except a
Cold-Air Intake and Drag Radial Tires. Record
11.52 120.21 Bone Stock except a
Cold-Air Intake and Drag Radial Tires. Record
Unfortunately he does not have C6 1/4 passes but you can get an idea compared to a C5Z. I would never go by magazine times.