Ok, Japanese, you win it...
NA you use the GS/AR/CB/ or MK to get it.
PAL you can get it at all.
For a little history thing, it appeared on the Japanese version, but PD didnt get to permission from Lamborghini to put it on, so all they did was remove the body and a few other things to where you couldnt get it, but some fine people that were really good at hacking, found the base codes and supplied us with the codes we needed. when the PAL version came out, it was fully removed from the game.