Crimson – The Color of Terror aka The Man with the Severed Head (1973),

Directed by Juan Fortuny and starring Paul Naschy is a bizarre mix of crime,
and euro-horror with a sprinkling of Frankenstein thrown in for good measure.
Centred on a gangster (Naschy) with a bullet lodged in his brain urgently in need
of a brain transplant and a mad scientist prepared to do the deed helped
by his lustful wife and you have a sleaze epic! Remastered from the
original negative and released on Blu-ray in July.