Hi,
Player has to drive to certain locations / shops / dealerships / barns to pick up car specific or rare performance and customisation parts. Cars can also be collected.
Players would have to transport the items using a pick up truck or a trailer back to their house / garage.
Once this task is complete the car part / car will be unlocked.
IMO this would give 4x4 and trucks a bit more purpose and usability within the game. It may also be more immersive than having the car appear instantly in the player garage.
Thanks for reading.