Black Cars

[GTP-SebringRace]

so is there any way other than the days 694-700 to unlock/buy the Black Toyota, Mazda, and Nissan Race Cars?

I just read this yesterday and I am on day 900 something!

 

[Famine]

No. They appear once every 700 days, on days 694-700.

This is by FAR the most asked question about GT4, along with "How do I unlock the GT World Championship", and an answer could easily have been found by looking for it (the FAQ stickies are a good place to start).