If you previously purchased the DLC, you can re-download it from your Xbox 360 Download History

The Racing Game of the Year Edition includes two discs; the second disc contains several car packs that can be installed directly to your hard drive.

Forza Motorsport 4 was released in 2011 for the Xbox 360. At the time, the concept of DLC was thriving, and Turn 10 Studios released several car packs and track expansions.