If it's the movie I think you mean the Willys wasn't black, it was grey primer. The other (bad) guy had an Orange Oldsmobile.
The 'good' guy did have a black Dodge at the beginning that he wrecked and used the engine out of it for the Willys.
That movie was a 'made for tv' movie in 1979. The name of it was 'Hot Rod' it was also sometimes called by an alternative name 'Rebel of the Road'.
(my favorite movie by the way!)
http://www.imdb.com/title/tt0079307/