I'm not familiar with the Brazilian cars but no,Aussie Chargers were not similar to 67-69 darts.
Aussie chargers were introduced in 1971 and ran through to 1978.
They were a short wheelbase coupe based on the VH series Valiant which is not common to any bodywork you have in the US.
The basic platform is,however, not too much different from your 67-76 A-bodies.
The R/Ts were 1971 and 72 only and sported the 265ci 6cyl with triple 45DCOE webers pumping out 302bhp.
The R/Ts are desirable and collectible (much like,say,an AAR cuda over there)and depending upon condition you would have to pay anywhere up to $200,000 for one.
A very nice R/T clone would be probably around $35k.
For $25k - $30k you can get a realy nice "ordinary" charger.
Probably around $5k - $7k for a rough project car.
Problem is,these things are popular and they have proven to be a fairly rusty model so good examples pull big $$$