Did some searching, most of the V8 stuff for $6000 is EB GLi's and such, or much older cars. You didn't mention if going nation wide is ok, so I did some Victoria only searching as you're in Melbourne...
Found this, might be good: http://www.carsales.com.au/pls/carsa...ch_distance=25
1995 Ford Falcon EF Futura: $6,200
247,000km, Cardinal Red, 4spd Auto
Seems decent. Dunno if you'd go for this car, maybe the mileage would put you off, but if I were in your position I'd get something like this.
Whatever you pick, best of luck