The Reds lie seventh in the southern hemisphere provincial championship's standings ahead of the final round of the season this weekend.
They will likely need to score four tries in victory over the 11th-placed Waratahs to secure a bonus-point win and a place in the post-season finals series.
Even then, the Reds' play-off hopes may still be dashed if teams above them on the ladder also score big victories.
Ioane and Gill are the only changes to the starting 15 that survived a huge scare from New Zealand's Highlanders side at Lang Park last week.
Lock Rob Simmons and back-rower Beau Robinson were also in the team named on Thursday, having been cleared to play after overcoming minor injury complaints.
Ioane, who recovered from a bout of pneumonia that excluded him from the Highlanders match, adds much-needed firepower for the Reds, who have struggled to post big scores in a season ravaged by injury.
"Combinations and cohesion are critical at this stage of the season and we've got the luxury this week of maintaining the majority of the squad while also injecting some x-factor through Digby and Liam," Reds coach Ewen McKenzie said on the team's website.
The Reds will also be hoping for a big match at Lang Park from mercurial fly-half Quade Cooper, who played his best match of the season against the Highlanders after being sidelined for most of it with a serious knee injury.