Do what has been done for countless generations of unlicensed racing games. Make the cars similar, but not exactly the same, change the logos, details, lights.
Check out
Tokyo Xtreme Racer 2 on the Dreamcast, it has around 400 unlicensed cars that can be very easily recognized, the game was very popular (recieved a US, Europe and Japanese release, later ported to the PS2) and they never got sued...
The exact amount of similarities or differences i dont know, but you can research a little bit more.
I did these for a game, changing the logo and several details on the cars and didn't have problems... yet
Check out the
nsx i made for the same game, the detail is lower and there are enough differences to stay safe for a low profile game.
The best route to take is to be brave and design your own cars. Use the parts you love most about your favorite models and get creative, that way you'll be safe and proud of yourself!