Cut out the side view of the car. Remove the bulk of the wood with the hand saw; then use the chisel and the block plane to slice off thin shavings until you are exactly at the lines drawn earlier. Make sure that the new faces of the block are flat and smooth.
A note and a warning: the blades of your chisel and your plane must be razor sharp, literally. They should be able to shave the hair off your arm. If the blades are blunt, pushing them into the wood requires too much force and you won’t be able to control the direction of the cut. Now the warning: make sure that you always have both hands behind the cutting edge of the tool. Never cut towards your hand or your body. Do not hold the workpiece with your hands while working on it with the chisel or the plane. Always clamp the workpiece securely in a vise. When someone else is using a chisel, do not reach into the path of the tool.
If the cutting edges of your tools don’t quite measure up to a samurai sword, and you don’t know how to sharpen them, you can find instructions for tool sharpening on the web.