There doesn't seem to be a car model in Radiant and porting a car from a different COD game results in only a part of the car such as the hood or the bottom of the car.

If you install the additional mod tools assets, it includes cars and trucks

If you want to download the Additional Mod Tools Assets, go into:

Steam>Library>Tools>(Right Click) Call Of Duty Black Ops lll - Mod Tools>DLC> and then put a tick on "BOlll Mod Tools - Additional Assets".