Might want to think about spacing them so they are above the space between the cars and over any workbench. You can then add lights over the cars to fill in the shadows.
I would also consider having multiple switches to turn on only the lights you need for the tasks at hand.
You wouldn't want the lights by the cars on when you know your gonna be working by the bench.
To work on the cars, I have retractable task lights for each car near the hood hung from the ceiling.
It's always good to have a light where your rolling toolbox is gonna park.
