The hood doesn't look right, does it? Let's fix that now. This is the complicated bit, because cars are complicated. Car bodies are not defined by the simple intersection of three forms that we've carried out just now. Cars want to be curvy! Curves are our enemy in SketchUp. Don't forget that SketchUp was initially designed for architects, and the nearest an architect ever gets to modeling curves is when they enter the annual RIBA fashion show for charity.
There used to be an advertisement going around where a guy made himself a VW Beetle lookalike from his old beat-up car, by getting an elephant to sit on the hood. Turns out this method is actually quite successful. I've chosen to show you how, in here. Remember, the model now represents the biggest dimension the car could get to, because you made it by tracing the very outside of the three car views. The real-life curved geometry of the car must sit somewhere within this outer box you've created. And...