Voyage to the Prehistoric Planet (1965) is an American version of the Russian movie Planeta Blur (Planet of Storms, 1962). The producer, Roger Corman, remixed the footage of the original film and added scenes with American actors. The movie is in the public domain and available on internet archive.
Roger Corman used the same Russian footage to make a second film (that’s efficient recycling) Voyage to the Planet of Prehistoric Women (1967), also in the public domain and available here or here.
For some comments about these films, you can read some articles on 1000misspenthours
