Wherever the stereo fitter put them!!

That was the 1st stop after you drove your new van out of the Holden dealer. Then you went to McDonalds, maybe the beach, your mates place, then eventually home....

Sorry, nostalgia caught me off guard again..... kick trims were common place for stereo speakers, but don't put them there!

Pull your rear panels off, cut a hole and stick them in there, one each side right towards the back.