GT5P used different display modes depending on context.
The showroom was the only instance in which it displayed at a native 1920x1080.
In game play was something like 1280x1080, using non square pixels, with the horizontal resolution stretched to 1920. Replay mode was a bit higher at 1440x1080.
No final word on the final version of GT5; maybe it's running higher since they've had an additional year plus to tweak the engine.
3D mode naturally will not match the same specs without something being compromised, whether it's frame rate, vertical resolution or whatever, but I'd be surprised if it was anything lower than 1280x720 @ 30 fps, which is hardly ideal, but playable.
I wouldn't be surprised if the actual 3D mode performed considerably better though.







