The opening song for this movie (and it is played again several times throughout the film) is from Lee Van Cleef's 1966 spaghetti western "The Big Gundown". Title is "Run Man Run", composed by Ennio Morricone, with lyrics by Audrey Nohra, and sung by Maria Cristina Brancucci.
Producer Ng See Yuen had a trouble with the local Korean producers in which led the Korean crew to quit the film with the exception of Hwang Jang Lee remained to fill the promise of the contract with Ng. Because of this, Ng ended brought Hwang to Hong Kong to give him more opportunities.