When I looked at a picture of a 1958 Buick (model unknown) in the movie Jägarna (1996), I noticed that you can tell what model it is by the lettering on the trunk/boot of the car. I don't know if most people already knew this or not, but on 1958 Buicks, each model had its own design found on the back. Here is a list of pictures of the designs found on each model:

Limited: http://www.ev1.pair.com/buick/source/buick_143.html
Roadmaster: http://www.plan59.com/images/JPGs/bu58rm7501.jpg
Super:http://www.motorcarportfolio.com/customer_images/3884_NTggQnVpY2sgcmVhci5- qcGc=.jpg
Century: http://farm4.static.flickr.com/3170/2551757786_93c50d3bb5.jpg
Special: http://www.theclassiccarshow.com/upload/CarImages/1370.jpg
Caballero (Station Wagon): http://3.bp.blogspot.com/_i_AovfzNXgQ/SCjtgA-g1gI/AAAAAAAAL5s/IDgzu4qeEe0/s400/IMG_1878.jpg