Originally Posted by: PTG Ace Ventura 
Copy the hood logo to the the right side of the car, insert all to the left side. It will be mirrored. Copy the mirrored left side logo over to the hood. Ta da, rinse, wash and repeat.
OR:
Make half the logo in the vinyl editor and save as a layer group. Go to paint a car and apply the layer group to the right side of the car. Tab over to the left side of the car and "insert all from right/left side". The image is now mirrored. Save the new half as a layer group. Exit without saving. In the layer group editor load both he original and the mirror and align properly. Save as new layer group
-- if wanted you may now go to "my layer groups" and delete the two halves as they take up space and you can always make the half from the whole.