Foyjur Rahman, 44, was accused of being one of the men who attacked Abdul Samad in Islington on 21 May 1997.
Mr Samad, from Bow, arrived in Alwyne Road with a bag of curry where he was set upon by two men armed with a knife and a meat cleaver, the jury heard.
Rahman was sentenced to a minimum of 18 years at the Old Bailey.
The jury heard the victim, who was also known as Kamal, was killed during a dispute between two Bangladeshi groups.
He suffered 18 separate injuries including a four-inch (10cm) wide wound to his waist, and died the following day in hospital.
Rahman was living in east London and helped to run a different curry takeaway in east Putney at the time.
The jury heard Mr Samad had been put under pressure to act as an "intermediary" between the rival groups.
The suspects plotted to kill the father of two by luring him into a quiet street after he refused to act as a go-between, the Old Bailey heard.
Mr Ellison said DNA and fingerprints found on masks discarded near the scene with the murder weapons matched Rahman.
Another associate, Mohiuddin Bablu, who fled to Birmingham then Bangladesh was convicted of the murder in 2012, he said.
The day after the killing, the 44-year-old went to New York.
He was eventually extradited in January of this year and arrested at Heathrow Airport.
Det Sgt Nick Miller said it had "taken many years and liaison with law enforcement agencies across three countries" to convict the men.
In a victim statement, Mr Samad's family said "not a single day that passes when Kamal... is not in our thoughts".
"It was no surprise to hear that, whilst he had suffered such horrific injuries, he warned bystanders to stay away as the men who had attacked him were dangerous," they said.
A curry house owner who lured a rival to a north London street with a fake food order then hacked him to death has been jailed for life.