Since no one has answered this part yet...
CSX3243 and CSX3255 (both street cars) were used in the movie, as well as a Butler replica.
I think that MrM posted a while back that the Butler had the extra vents.
... interesting to note that a recent picture of CSX3255 shows it has the square vents on the hood as well. The owner may have added them to match the replica in the movie.
Bill's the master of trivia on this movie, however....