I find scale drawings of cars to be the hardest to obtain of any genre of model subject. I have had to do my own for a number of scratch projects. Fortunately digital photography and cheap CAD programs have made this feasible if you can find a prototype to photograph.
There was one car magazine that when it reviewed cars and trucks at least included a side elevation drawing. Forget which mag, but it is one that goes way back. Next time I am at the library I will see if I can find it. There is a british company that offers scale drawings of ships, cars and other vehicles, that used to be available through Dromedary, but I have not seen anyone else offer those in US after dromedary went out of business. And, their car drawings were only classic, historic car subjects.
So, as I say, you are generally on your own resources. Still, those cars are probably more available to find than historic airplanes or ships.