A third victim, 76-year-old Maureen Suckley, had jewellery torn from her wrists after he forced his way into her home days earlier, surviving because she did not put up a fight.
Judge Clement Goldstone QC, the Recorder of Liverpool, said Mrs Leyland and Mrs Biddolph "paid with their lives for their brave resistance".
Flood, a former plumber, had debts of £18,000 and was so short of cash he sold a console and games belonging to his children. He was also facing a demand for £500 rent arrears.
He knew where Mrs Leyland and Mrs Biddolph lived having driven them around on shopping expeditions.
Flood first targeted Mrs Suckley, taking her gold wrist watch before threatening to kill her cat if she did not hand over cash.
Two days later he killed Mrs Leyland, leaving his footprints, DNA and fingerprints at the scene. Her jewellery was found in his possession when he was arrested.
Apart from being strangled she had suffered bruising and fractures to her ribs.
Mrs Biddolph, who lived half a mile away from Mrs Leyland, was found in the upstairs bedroom of her home with a telephone charger wrapped three times around her neck.
After killing the women and going to the betting shop, Flood began drinking heavily before ringing wife Carol to confess he had "killed someone".
That afternoon he was arrested, drunk, at Southport police station after trying to push his victims' jewellery through a gap in the enquiry desk. He told officers he had killed two women earlier that day.
Sentencing Flood, the judge said: "You knew these women because you were employed as a private hire taxi driver.
"They had entrusted their safety to you and I am satisfied you targeted them because they were vulnerable, they had money and they lived alone.
Mrs Biddolph's daughter Anne Pearson said her mother was a "lovely caring person who always thought of others before herself".