Hi Ian,
I have a rb25 hi-flow with a VG30 upgrade. Mine is up for sale ($1100), but i would not sell it to you as these turbos are not that responsive and when approaching boost, comes on hard [ie: A lot of fun, NOT good for a family car]. Experienced track drivers have looped/spun my car due to it's boosting characteristics. I am telling you this to state that any/all hi-flows are not the best option, that is why i am replacing mine with a HKS GT-RS. Refer to attached pic. Pete has the same turbo, in his R34 GTT, with the best tunning, but still acts in a similar manner.
Silva33 has a HKS 2535 that would be best suited for your needs, he also lives in Melbourne and has just posted it for sale @ $1500 (with HKS Actuator) or $1300 (with std rb25 Actuator). This is a great turbo, as the power is progressive, thus being safer. The price is honestly awesome too, if he sold this 1 month earlier i would have saved myself $1400 .
Silva33's Turbo: click here