Eamonn Sheridan comes in for Chris Cochrane on the left wing, while, in the two other changes to the back-line, Ireland will line out with new half-backs in Ian Madigan and Ian Porter.
There are switches in the second row and back row with Eoin Sheriff and team captain Paul Ryan making way for Ian Nagle and Michael Entwistle respectively.
In Ryan's absence, his Leinster colleague Eoin O'Malley will captain the side.
New Zealand roared to a 48-9 win over Tonga in their opening game of the tournament and showing the strength of their panel, they have made 11 personnel changes for the Ireland game.
One of their new men in is giant prop Ben Afeaki, a veteran of two Under-19 World Championships, who weighs in at a colossal 21 stone 8 pounds. Ireland's heaviest front rower is UCD and Leinster's Ben Barclay (18 stone).
Elwood said: "Any competition you go into with New Zealand, they're going to be number one seeds or favourites.
"We put in a great performance against Argentina. I thought there were a lot of positives in the game in that we tried to play rugby, tried to play our brand of game.
"We matched them physically, which historically is a strong part of the Argentinian game. There were a lot of positives in it.
"Obviously the big negative is that we lost the game. We played some good rugby but we didn't get the result we wanted."
Recovering and getting rid of the bumps and bruises over the weekend, Ireland will take a positive outlook into tonight's game against the tournament favourites.
"As I said to the boys last weekend, we've just got to dust ourselves down. We're in a very tough pool and it doesn't get any easier playing the World champions," Elwood added.
"I've told the boys we're going to try and play our game, obviously try and counteract New Zealand and how they want to play.
"The guys are relishing the opportunity to play against the best team and the best bunch of guys in this age group."
Just as he has done for every game of his two years at the helm of the Under-20s, Elwood will again ask his young charges to go out and express themselves tonight and play to the best of their abilities.
Together with manager Phil Orr and assistant coach Dan McFarland, the former Connacht and Ireland out-half has prepared the squad thoroughly for this game - one which will effectively decide where the Irish will feature in the knock-out stages.
"Obviously we watched New Zealand v Tonga. I know it wasn't their full team, they've made 11 changes for our game.
"But we can only play what's in front of us. We've done our analysis of New Zealand as best we can and are going to try and counteract them.
"I've always encouraged the guys, the mantra all year has been just express yourself, try and play ball. But obviously it's very important to try and play winning rugby," he insisted.
"If we can adapt to what's put in front of us against New Zealand, then I just hope the lads give it their best, play 100% and that's all anybody can ask."
Elwood's opposite number, New Zealand coach Dave Rennie, is expecting a good, competitive game from the Irish.
"We sat there and watched Ireland's game (against Argentina) and they'll be disappointed, they should have won that game but they couldn't quite put away their chances," he said.
"They play with a lot of endeavour, they're physical in the forwards and their backs play a nice wide game with good distribution.
"So we're aware aware of that and hopefully we can eliminate those threats and create turnovers from those situations."
Tonight's game, which kicks off at 9.10pm at Cardiff Arms Park, will be shown live on Setanta Sports Ireland, S4C and British Eurosport 2.