The Dunedin-based side will meet the winner of the semifinal between Waikato’s Morrinsville and Taranaki’s Tukapa.
Covid-19 has created a few scheduling problems, but the final is expected to be held on November 6 or 13.
The venue has not been confirmed, but the game will be played as a curtain-raiser to a NPC game.
Bush Pigs manager Thomas Grant said the key to the side’s success was a tremendous opening half and some staunch defence in the second spell.
Southern’s Jack Leslie opened the scoring with an early penalty and not long after fellow Magpies team-mate Josh Buchan danced through a gap to score from 15m out.
Riku Kitahara added a second try after a break from replacement halfback Charlie Marsh.
The visitors led 17-0 at halftime but conceded an early penalty and spent a good portion of the remainder of the game defending.
The defence was broken once, but Aaron McMurray scored with under 10 minutes remaining to help clinch the win against the Wolves.
Bush Pigs prop Waiora Morris had an outstanding game and loosie Wilson Driver got through a lot of work on defence.
