Here is a better set of pictures for you. This is the correct light, there are many shorter versions which are much more common as they were available across the GM product lines.
https://www.flickr.com/photos/advance-design_parts_co/16783518929/in/album-72157631868452754/
https://www.flickr.com/photos/advance-design_parts_co/16969714735/in/album-72157631868452754/
Here is is an example of the more common car mount style (Oldsmobile in this case).
https://www.flickr.com/photos/advance-design_parts_co/11597022005/in/album-72157631868452754/