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1,2,4 - while the angular look works sometimes, I assume these weren't all taken on hills, I might stick with a flatter perspective even if that means rotating the image in post.
I really like 3 as is, though you might try a slower shutter speed even for front 3/4 shots (maybe 1/320-1/640, enough to get a little blur into the wheels without sacrificing much sharpness on the car). For the rest, consider the "rule of thirds" and loosen up the crops, grab more sky and "race track scenery" maybe. They're all cropped real tight and real "centered". Try and leave "somewhere to go" in your crops, typically I crop a race car to the 1/3rd point that leaves 2/3 above the horizon line and 2/3 from the center line of the car forward so the car has open road in front of it.