A proper exclusive save game will have these cars sitting in your garage, pristine and ready to drive. Without the save, they are just ghosts in the game code.
Forza Horizon 1 was originally an . It was not released on PlayStation or PC at the time. However, regarding save games and "exclusivity" of playability: forza horizon 1 save game exclusive
Here’s a well-structured, informative review for a Forza Horizon 1 save game that’s marketed as “exclusive” (e.g., 100% completion, rare cars, max credits, or special unlocks). A proper exclusive save game will have these