You're right (I only noticed the year directly following the title in bold), but it's also stated that they were ready to film in march '63, but the works were postponed due to incompetence of a Spanish producer
It's getting complicated, I'll do some more research tomorrow
Maybe it's safe that the film was not made nor released in '62 or '63
For the moment '64 as year of production seems the best candidate, '65 the best candidate for year of release
But where did Bruckner get his dates ('63 production, '64 release) from ?
By the way, Silver Wolf is right, westerns, or western-like movies, have been made in Italy since silent movie era, as the first 'fullblood' western however, a film from 1941 is often cited, NOZZE DI SANGUE by Goffredo Allessandrini
I'll do some research in this area too