It was probably a miracle that this movie was even completed - the studio tried to bury it. In fact there is a persistent rumour that the original 'long cut' master tapes were buried by the self same studio bosses under concrete in part of the M4 (or was it M25?) motorway to the West of London. I remember the fuss that accompanied the unearthing of extra footage for the 'long' version of the film back in the mid 80s. It was heavily cut for US distribution (for drive-ins) back in the 70s. I have a copy of the latest 'Director's Cut' and the long version enclosed with that was obtained in the US from the collection of Roger Corman, I think (a miracle). Until this was unearthed the extra footage was presumed lost under concrete.
The folk music used in the film had an equally weird history. Tapes were unearthed by chance from someone's attic in Swindon, Wilts. so I've heard.