Umar Arif, 29, was arrested after police seized 40kg (88lbs) of the drug in 2014, Cardiff Crown Court heard.
Khalid Yassen, 30, of Cardiff, was cleared, but the jury could not reach a verdict for Umar Butt, 26, of Cardiff.
Yesterday, Shazia Ahmad, 38, and Wasim Ali, 29, both of Newport, and Zawed Malik, 41, of Greater Manchester, were found guilty of the same offence.
The court heard 37kg (81lbs) of the class A drug was found inside a speaker and a suitcase in a car stopped on the M5.
Another 3kg (6lbs) was discovered in the footwell of a taxi in Newport.
The group stood to make more than £270,000 in profit from the drugs, the trial heard.
Other group members, Mohammed Sajjad, Imtiaz Ali, Paul Anthony Thomas, 42, of Cardiff, Waseem Mohammed Riaz, 28, of Newport, and Mohammed Aftaab Boota, 27, of Newport, previously pleaded guilty to conspiring to supply heroin as part of the same plot.
Tracey Ford, 39, of Cardiff, admitted money laundering.
Sajjad, 38, from Cardiff, and Ali, 35, from Newport, were described in court as the "generals" running the operation.
Between them, they owned 35 phones and were said to be "experienced drug dealers".
Both men had been convicted twice before for supplying drugs, the court heard.
A man from Cardiff has been found guilty of conspiring to supply £5m worth of heroin.