as production on "barbarella" wound down in october 1967, director roger vadim began shooting his episode of the omnibus film "spirits of the dead", which co-starred peter fonda and jane fonda. it was during the making of this film that peter fonda told southern of his desire to make a 'modern western' in which motorbike riders substituted for cowboys, a concept that had been largely inspired by the success of roger corman's influential low-budget "exploitation" biker films "the wild angels" (1966) and its follow-ups, in which fonda and his close friend dennis hopper had featured. fonda pitched his idea to hopper on his return to america, and southern added his weight to the project, agreeing to work on the script for scale ($350 per week).