you could go for a turbo setup, but keep in mind that for $4200 you get something like 70-80-90kw more at the flywheel (157 to 230/240) without resorting to forced induction. if you have another $4000 or so, get the turbo. with that setup, you'd end up with an easy 300kw+
lets just say you also get some 17x8" wheels and upgrade the suspension ($2000-2500). if you start with a stock 6 falcon (one just like mine) you'd end up with a HSV beating Ford 6 for around $41,000-42,000. not bad, ay?
of course, your next major expense would be the gearbox because there's no chance in hell that either the T5 or BTR 4 speed would cope with that much power reliably.