Is this the one? I bet it is. Very good movie too.
"Thunder Road" starring Robert Mitchum
The film was based loosely on an incident in which a driver transporting moonshine was said to have crashed to his death on Kingston Pike in Knoxville, Tennessee somewhere between Bearden Hill and Morrell Road. Per Metro Pulse writer Jack Renfro, the incident occurred in 1952 and may have been witnessed by James Agee, who passed the story on to Mitchum.
In the film, Mitchum drove a hot-rodded 1951 Ford 2-door sedan with a custom tank in the back for moonshine and later a 1957 Ford coupe with the same alterations. The '51 Ford was modified with a '49 hood and grill and with the rear taillight trim removed. The film's dialogue refers to the car as a '50, but it is not, although at least one exterior shot, when the car spills oil on the road, is of the trunk of a '50.
Most of the scenes were filmed in Asheville, North Carolina and some at Lake Lure.
The movie's theme song, "The Ballad of Thunder Road", was later recorded by Mitchum and became a popular single record, although Mitchum's rendition is not the one in the film itself.