Even if you could find a BMW v8 in Australia, the initial price, and cost of installing would be WAAAAY top heavy,
Anyone down here that wants to go V8, should not go past a 4 litre Toyota, can be picked up for $1500 ,Drop in easy, this is a great engine,Technically 100 years ahead of the Rover, Unlimited parts availability here in OZ, As light as the Rover, with 3 more cams, and 16 more valves.
The P76 was last manufactured 32 years ago, that's a giant step backwards.
And As I pointed out to Bushie on ClassicZ, Rover,Primative,thirsty, English rubbish, named after a dog.