Back to he cars. If you are going to capture the essence of that car you need to feature the lights and some of the grille. Even if there is no grille...like with a VW or Porsche...you need to show the eyes of the car.
The Plodge* that you see on the heading image is a 30's car, and those lights are complex glass sculptures that need careful lighting - no pun intended - to bring out the patterns. Lucas lights and other spot lights may also need extra illumination to show the center bulb structure.
The choice of flash in this case meant that the shadows caused by bright sun light could be filled in. Any dedicated TTL flash works well for this if it is on the appropriate body. You can even use one that is not TTL as long as you can adjust the output somehow and fire it from the camera. This image used a Fuji X100 and Nikon Sb 700 flash and worked fine.
If your car owner can turn on the headlights, and if you are photographing it at dawn or dusk, so much the better. If not, you can always fudge it a bit in Photoshop.
Go towards the light...
* Dodge with Plymouth components. A particularly Australian variant, made in Adelaide.