During the development of LEGO Ghostbusters Ecto-1 (21108) model, designer Marcos Bessa also created a great looking 1959 Cadillac Miller-Meteor in black. This is the original car that the Ecto-1 is based off of.
If you own the Ghostbusters set, it’s a fairly easy modification to make provided you have the pieces. You’ll need to swap out all the exterior bricks to black & dark gray ones and remove the stuff on the roof. The result is a classic patrol car that can go well with any classic setting.