Ideal RPM I've around is around 5,5-6,500, that's with 350rwkw and semi's also.
Totally depends on the surface, tyre temp etc
8,000rpm is too much, you'll just sit there tyre turning for no real gain with undue stress for that brief second where power is transferred before wheelspin breaks out.
Ensure your wheels are straight too, if they are turned slightly it can lead to you smashing the front stock diff's while the car scrambles to work itself right.