Smith and Heller - members of the World and Rogue chapters of the gang, respectively - both pleaded guilty to supplying the Class A drug, possession for supply, and participating in an organised criminal group.
Smith also admitted an additional charge of manufacturing methamphetamine.
At a sentencing hearing in the High Court at Hamilton in August, Smith and Heller were both placed in the second-highest category of meth offending based on the quantity of drugs the police proved they were culpable for.
With 988g, Smith had a starting point of 12 years and four months in prison.
The starting point for Heller, with 868g, was 10 years and six months.
Justice Grant Powell gave both men the full 25 per cent discount on their prison time for pleading guilty early, then added significant reductions for dysfunctional childhoods which led them into lives of crime.
Psychological and cultural reports prepared for Smith outlined a significant history of abuse growing up in state care and foster homes, as well as first using methamphetamine when he was 15.
That left Smith "functionally illiterate", said Justice Powell, making him dependent on drugs and alcohol and introducing him to criminal associates and the Mongrel Mob.
He also appeared to be suffering from Post-Traumatic Stress Disorder and the ongoing effects of a brain injury.
"While I cannot accept that the operation itself was other than a large-scale commercial operation, I agree [with Smith's lawyer] that the catalogue of issues addressed in the various reports significantly reduces the level of your culpability with regard to the offending," Justice Powell said.
"The reports together paint a compelling picture of what can only be described as
horrific background circumstances that cannot but have played a significant causal
role in your overall criminal history as well as the offending for which you are being sentenced."
Smith received a further 25 per cent discount for his relevant background and another 5 per cent to assist his rehabilitation.
On top of the 25 per cent discount for the guilty plea, this brought Smith's final sentence to five years and six months in prison.
Cultural and psychological reports were also prepared for Heller which painted a similar story of abuse in state care, drug and alcohol addiction, leading to poor mental health.
"Those same experiences likewise introduced you to criminal associates from a young age, including the Mongrel Mob, and although not formally diagnosed, there appears to be a more than credible basis for considering that you too suffer from Post-Traumatic Stress Disorder," Justice Powell said.
On top of the 25 per cent discount for the guilty plea, Heller received a 15 per cent discount for his dysfunctional childhood and another 15 per cent for rehabilitation to bring his prison time to four years and nine months.
"Perhaps for the first time, you have started to look outside the criminal horizons that have framed your viewpoint for so long and while you recognise it will be a difficult and slow process ahead, there is a chance at a different life and now is the time that you want to move towards that place."
In July, the enterprise's lead investor Michael Ormsby was sentenced to three years after admitting money laundering and cannabis offences.
He also received discounts for his remorse and rehabilitation prospects, as well as a difficult childhood.
Police found $30,000 in Ormsby's bedroom when they raided his property in December 2020 and analysis of financial records showed cash deposits of $164,891.33 through various companies linked to Ormsby over the previous three years.
"You were able to distance yourself from the manufacture and dealing, while profiting from the operation," Justice Gerard van Bohemen said.
Operation Gulfport was part of a series of police investigations in 2020 by the Waikato organised crime squad, led by Detective Senior Sergeant Steve Ambler, which targeted the Mongrel Mob.
Those charges are unrelated to the prosecution of three members of the Waikato Mongrel Mob, alleged to be involved in serious drug dealing and money laundering offences following Operation Equinox, the New Zealand offshoot of the global 'Anom' sting investigation.