This is a paid asset, but now you can download Complete Vehicle Pack V2 Free.
Detail this asset from Unity Store: Original Link
Complete Vehicle Pack V2 v1.4 (Latest version)
Check out the first volume of this package
Complete Vehicle PackThis package contains 36 different vehicles, varying from ordinary town cars, to trucks and helicopters.
It’s suitable for racing or delivery simulators, or top-down games.
The package contains 43 prefabs, 36 vehicles, 2 crates, an attachable trunk and 4 extra wheels, for easy customisation.
All models share the same material and texture, a 4096*4096 atlas, for optimum performance on mobile devices. The polygon count for each model is around the 1k mark and each vehicle has separated wheel meshes. All the models have a custom mesh collider.