Ben Barclay returns at tighthead prop, coming in for the benched Stephen Archer, while an ankle injury to Patrick Mallon sees Michael Entwistle promoted to the back row.
Used as a replacement against Italy, Entwistle will start the Scotland game at openside flanker, with Mallon's absence at number 8 seeing team captain Paul Ryan shift to a blindside role and Kieran Essex is moved to the base of the scrum.
Ciaran Ruddock, son of former Leinster and Wales coach Mike Ruddock, also returns to the matchday 22, having come off the bench in the pool defeat to New Zealand.
The Under-20s are hoping to end the inaugural Junior World Championship on a high with their third win on the trot. In the past week, they have beaten both Tonga and Italy.
No strangers to playing Scotland, Ireland beat their Celtic rivals 17-12 at Dubarry Park in this year's Six Nations championship, while in a warm-up game for this tournament, played at Ravenhill, Elwood's charges claimed a 41-27 win over the Scots.
Although there may be a slight change in personnel, these sides also met in last year's IRB Under-19 World Championship (at Ravenhill again) with Ireland emerging as 13-12 winners.
Looking forward to the Newport encounter, Elwood said: "We know Scotland will be after us because we've already beaten them twice this year.
"We beat them in the Six Nations and then in a warm-up match in Belfast so we're eager to make it a hat-trick.
"As soon as we were knocked out of the pool stages, our goal was to win the final three matches.
"We're two steps there now and it would be great to finish the tournament on a high."
IRELAND UNDER-20 TEAM & REPLACEMENTS (v Scotland U-20s, IRB Junior World Championship, Sunday, June 22, Rodney Parade, Newport, kick-off 1pm):
15 - Niall Morris (Blackrock College/Leinster)
14 - David Kearney (Lansdowne/Leinster)
13 - Eoin O'Malley (Old Belvedere/Leinster)
12 - Conor Cleary (Greystones/Leinster)
11 - Chris Cochrane (Queen's University/Ulster)
10 - Martin Dufficy (Dublin University/Leinster)
9 - Ian Porter (Queen's University/Ulster)
1 - Paul Karayiannis (Queen's University/Ulster)
2 - Jason Harris-Wright (Greystones/Leinster)
3 - Ben Barclay (UCD/Leinster)
4 - Ian Nagle (UCC/Munster)
5 - Eoin Sheriff (Lansdowne/Leinster)
Ireland Under-20s 9 Italy Under-20s 6 (after extra-time), Wednesday, June 18, Cardiff Arms Park