Your
redline is at 7400 RPM. This is the maximum RPM you should ever intentionally put on the engine.
The rev-limiter is at 8000 RPM, and is just there to save your a$$ in case you make a mistake (like miss a quick shift). It is NOT GOOD to hit the rev-limiter; it shuts off the fuel injectors which leans out the mixture for a couple of cycles usually giving you a couple of hard detonations - at 8000 RPM! Not the most healthy thing (although it's still better than overrevving and throwing a rod). This is why they give you a 600 RPM cushion past redline; it's not there for you to use intentionally - it's there to protect your engine.
Also - you shouldn't be powershifting with only the stock rev-limiter in place (for the reason above). If you must powershift, pick up a decent aftermarket ignition system with a "sequential rev-limiter" - and set it for something like 7700 RPM. This will drop sparks, not fuel. You'll bang into a rich condition, not a lean one; the engine won't detonate and it'll recover faster.
