Check out this '68 Wildcat Police Cruiser! :TU: David http://images8.fotki.com/v131/photos/4/42477/1574301/68mshp-vi.jpg
I have photo of a 1955 Buick police car. I have no idea if its real and i forgot where i found it. Enjoy!
This 55 was featured in Collectible Automobile a few years ago. It is supposed to be the last remaining of the California Highway Patrol's 55 Centurys. It has a two door sedan body from the Special. This body style wasn't available in the regular Century line but since it was the lightest body, they used it in the Century police car. This car is also supposed to have the larger Roadmaster brakes.
And they were all sold to the California Highway Patrol! I thought there only one remaining but this article from the Buick Bugle says there are probably 4 remaining. http://www.highwaypatroltv.com/BuickBugle1997a/
I've seen a few pictures of late 60's/early 70's Buick police cars. I can't imagine there were many Buick (as well as Olds & Mercury) police cars sold because they would have been more expensive than the common Chevy, Ford & Dodge cop cars, and most dept's go by cheapest bid. I do remember reading that Buick supplied cars to the Flint Mi police dept so they could get some real world endurance testing results.