Yassar Yakub, 28, was the front seat passenger in one of two cars travelling in convoy when four unmarked police vehicles surrounded them at junction 24 of the motorway in Huddersfield.
He was shot at 6.05pm on January 2 last year after an undercover police operation in which officers from West Yorkshire had been deployed to observe individuals including Mr Yakub, a jury at Leeds Crown Court heard.
On Friday Mohsin Amin, 32, who was driving the car, was convicted by a jury, following a two-week trial, of conspiracy to possess firearms with intent to endanger life.
Two other defendants, Rexhino Arapaj, 28, and David Butlin, 39, were found not guilty of the same charge but Butlin was convicted of possession of an offensive weapon, a push-knife.
Mr Arapaj nodded to the jury as he was released from the dock, dragging a suitcase behind him.
Mohsin was remanded into custody and Butlin was bailed until both are sentenced on Wednesday.
Possession of a firearm with intent to endanger life carries a maximum sentence of life imprisonment.
Mr Justice Turner warned Butlin that allowing him bail was “no indication” of what his sentence will be.
The court heard how the officer who fired the fatal round saw Mr Yakub holding a weapon, and felt he was an imminent danger.
All three defendants were monitored by police travelling from the Cedar Court Hotel in Huddersfield to Cafe de Akbar in Leeds Road, Bradford, with Mr Yakub in the passenger seat of a white Audi A4 being driven by Mohsin, while martial arts coach Butlin drove a white VW Scirocco with Mr Arapaj as his front seat passenger.
Mohsin and Mr Yakub entered the restaurant - with the Scirocco parked outside - and dined with two men, Mohammed Nisar Khan and Kashif Tahir, for around 70 minutes, the court heard.
Prosecutor Peter Moulson QC told jurors it was significant that Mr Yakub had entered the restaurant carrying a bag and left more than an hour later with the same bag, but wearing gloves.
After the meeting, the two vehicles travelled towards Huddersfield, when they were suddenly stopped by police who found a fully loaded and operational Russian Baikal pistol under the passenger seat of the Audi.
Officers also uncovered a silencer and a bag of plastic ammunition in the glove compartment.
Police later discovered a string of WhatsApp messages between Mohsin and an unidentified man, known as Raa, leading up to the day of Mr Yakub’s death.
Mohsin, of Broomer Street, Dewsbury, Arapaj, of Thornlea Road, Huddersfield, and Butlin, of Huddersfield Road, Holmfirth, had denied the offences.