Santo And Blue Demon vs Dr Frankenstein (1974)

aka: Santo Y Blue Demon Contra El Dr. Frankenstein

Innocent women are being kidnapped and used as guinea pigs for a brain transplant experiment as Dr. Frankenstein continues his quest to perfect the brain transplant operation to bring back his deceased wife at any cost–even if it means paying with the lives of others. El Santo and Blue Demon are called in to help when their friend, Alicia (Sasha Montenegro), becomes Dr. Frankenstein's next target. (In Spanish language, with English subtitles).