I don't remember seeing this classic when I was young. I won't go too far into the background of the movie.
Suffice to say Robert Mitchum co-wrote and starred as a moonshine "transporter". His son James plays his younger brother. Gene Barry is a "revenuer".
But this is about cars. Hopped up cars. Mitchum at first is driving what looks to be a '49 or '50 Ford Tudor sedan. As I've researched it, it's actually a '51 Ford with a '49 hood and a '50 grille and likely a '50 front clip. The taillight area gives away the '51. On the hood you can see where F-O-R-D is removed so that would be a '49 and the front turn lights would suggest a '50. Regardless, it's cool.
Later, he is driving a '57 Ford Fairlane 500. Lots of '57 Fords and '57 Chevys in this movie.
I've included a few pics from the movie.