I'm not an attorney, but I do deal with copyright law in my job with the California Supreme Court pretty frequently, and I'd have to say that you're on very shaky ground here.

If your photoreal textures include the Ford or Pepsi logo, you can't reproduce them for profit without permission (the written kind) from the trademark holders.

Now, if you're just taking photos of a car with all of its bumps and flaws and using that as texture for your car, you don't owe the car maker anything, as you're not infringing on their copyright.

I'd go as far as saying that if you make a car model that's unmistakably a Mustang or Bently or Model-T you may be infringing on copyright of the design, but the likelihood of one of the companies suing for that is minimal, as you're not actually competing with them using their design.  Major movies get clearance from automakers to use their cars in a film.  I worked on a cheezy horror film many years ago and Chevy refused to let us show their cars in a horror flick.  So, every car driven in the movie is a Ford, because they let us use the cars.  Likewise, every beer consumed in the movie is a Miller product.

Hope that's at least a little helpful.  I'd just say be very careful.