GT5 Prologue gets content boost and split-screen racing for US
While SCEE's promising an imminent announcement of GT5 Prologue's date in Europe, the Americans have been thrown a rather large bone with news that the US version is going to receive decent content addition over the Japanese release.
According to this, the American disc will include split-screen racing, a Drift Mode and car tuning. We haven't seen the Japanese release, if we're being honest, so we're not sure if tuning was included previously.
[Update: We've just been told that there definitely wasn't tuning in the Japanese version - Ed]
The five tracks from the Japanese version are included, and the High Speed Ring has been added. Each track has two layouts.
There's a full list of cars - there are more than 60 of them - through that link.