Welcome to Just Commodores, a site specifically designed for all people who share the same passion as yourself.
If you want to go fast do your research and get bits that go together well, not just a mixture of off the shelf bits. If i were you I would be going down to a reputable performance shop and telling them what you want from the car (not a power figure) ie qt et, track, dyno queen, etc etc. You may get 300rwkw but with non compatible or unsuitable other parts you may not get it to the ground, or break the car, or run into ancillary problems such as having to upgrade fuel or intake or gearbox etc etc etc. At the end of the day going into a shop with your budget and a good idea of what you want will be best I'd say. Any good shop will be able to put together a RELIABLE and SUITED package for your needs in your budget.