They will be accused of murdering father-of-two Roy Collins (34) in April 2009.
A source told the Herald: "Steve Collins will be a central link for the prosecution when this case comes to court.
"He will be a star witness. The option of giving evidence by video link is there but knowing the measure of the man I fully expect him to take the stand in person."
The shooting of Roy Collins sparked national outrage.
His father Steve and his family – who lived under constant threat of attacks – were eventually forced to flee the country last year.
One man, James Dillon (26), has already been jailed for life for the murder.
However an intense garda investigation has continued since his trial in May 2010.
Last July a loaded semi-automatic Glock pistol – believed to be the weapon used in the murder – was found near railway tracks in Rosbrien in Limerick.
The location is near where the Mercedes car used by the killers was found abandoned and on fire on April 9, 2009.
A man cutting grass on behalf of a local rugby club discovered the badly-rusted Glock pistol.
The two Limerick criminals, Wayne Dundon (35) of Lenihan Avenue, Ballinacurra, Limerick, and Nathan Killeen (22) of Hyde Road, Limerick, are expected to be brought before the Special Criminal Court for formal charge tomorrow.
Dundon and Killeen are both currently imprisoned for separate offences.
Mr Collins – who was on the scene of his son's shooting within seconds and craddled him as he died – will be offered the option of giving his evidence by video-link.
However, it is understood that Mr Collins will opt to take the stand in person instead.
Roy Collins (34) was shot dead outside his family's arcade business at the Roxboro Shopping Centre in Limerick.
In May 2010 James Dillon (26), originally from the southside of Limerick, was jailed for life for the murder of Roy Collins.
However, gardai remained determined in their pursuit of those who ordered the hit and the man who was seen in the getaway car with Mr Dillon.
In March 2012 Steve Collins vowed to see justice done for his son, a father of two young girls.
"I am determined to see justice done for Roy and to see this through to the end," he said.
In the interview, Steve told the killers: "I'll be back to see you all jailed. I will be coming back as a witness for any further murder trials."
Mr Collins and his family have lived in constant danger from Wayne Dundon and his vicious mob since their son Roy was gunned down at the family's business three years ago.
Gardai yesterday made an application to the Special Criminal Court for the production of the two Limerick men before the same court tomorrow.
They will be brought under tight security to the court to face separate murder charges.
Roy Collins' murder occurred four years after members of the Collins family testified against feared criminal Wayne Dundon.
In 2010, gunman James Dillon (22) pleaded guilty to Mr Collins's murder and was sentenced to life imprisonment.
However, when questioned by gardai, Dillon refused to identify who ordered him to carry out the shooting.