I suppose the question we should as is... Why do you want to make 300rwkw? Because if you want to go faster, or the car to handle differently, there is obviously other ways of achieving it other then power mods, as in, you are already pulling the amount of power that some of the guys on here are pullin, and make mid to low 11 second passes.
Other then heads (which would be a good idea none the less) I would definitely look into getting a set of 3.9 diff gears, improving your acceleration, will handle differently too.
And as stated before, a hi-stall.. how much is up to you, they are making good ground with dev in this area and are currently making GOOD 4,200rpm full lock-up stallies that are not a pig to drive at all.. and are currently supporting your sized cam as well..
Those two mods, plus a good set of sticky tyres and you should be seeing some decent 11second times..
But in saying that, if you want more power for the wank factor, go to a happy dyno and laminate the print out.
Or go forced induction, which would definitely be pretty good fun too...
All depends on what you want, and why you want 25rwkw more...