By the time you add up all the costs of purchsing the engine, and all related parts, packing them up for overseas shipment, securing them in a container, and then the cost of shipping, plus the cost of the naturally aspirated vehicle down in Australia, you might be better off having someone sell you a 300DT for about $3K or so and shipping the entire vehicle down there.

I have no idea about the shipping cost, but, let's say it's $2K.

You have a decent 300DT for $5K.

Now, you sell the 300D for $2K (just guessing what it might sell for down there).

Your total cost for the new vehicle is $3K.

I don't think you can purchase all the parts, ship them down there and pay yourself a reasonable amount for your time to do the conversion and stay anywhere near $3K. Additionally, the risk of not having the proper parts, and being unable to get the proper parts, is significant.