Kaierau's front row of youngsters Jack Yarrall and Joe Edwards, along with Isaac Johnson, had a tough assignment against the Ruapehu veterans in Karl Parker, Roman Tutauha and Kim McNaught, but they more than held up their end for the duration.
No8 Campbell Hart created a lot of chances for the home team with surging bursts, but the ball often went down or the key final tackle was made - Kaierau flanker Cade Robinson keeping busy.
The momentum fluctuated throughout as Kaierau scored three rapid tries in the second quarter to lead 21-7, before Ruapehu hit back twice to close the gap to two points.
Having already run 55m for his first try, Saurara repeated the effort right on halftime from a quick tap, before Ruapehu tied the match up with their fourth try early in the second half.
Both teams then traded seven pointers, with both conversions by Malo and Ruapehu fullback Andrew Evans coming from the sideline, to set up a pulsating finish at 33-all.
Nerves showed as each side gave the other golden opportunities to beat them - for the next 7-minute stretch there was a constant stream of turnovers, dropped passes and infringement drawing the whistle of Noah Viliamu.
Kaierau got the decisive call in their favour from 33m out and Malo surprisingly handed the kicking duties to Saurara, who nailed the matchwinner.
Hart had one last chance to rescue the game for his team with a powerhouse charge down the sideline, but Ethan Robinson and reserve Dominic Broadhead shut it down.
Delighted Kaierau coach Denis Edwards said Saurara often went his own way a little too much, but the young man's pace certainly made it pay off.
"He played well. With more games there, he could be a halfback."
There is still work to do on Kaierau's one-off tackling, but Edwards knew winning a thriller, away from home, was a result which can make a team.
"[Ruapehu] played a different game than what we expected.
"They hung in there, we could have just folded.
"The guys, they really had to learn to dig in. That's money in the bank for future experience."
Ruapehu assistant coach Peter Rowe said having brought up a lot of younger players this season, their traditional phase-orientated game plan had to change to reflect the new line-up, and they were learning to be expansive and use width.
"It was a big improvement, from our point of view.
"Just disappointing it was going to be one or two points, when we missed our opportunity down there [at the end]. It was just the little things."
Ruapehu drew first blood as they took a 10m penalty scrum for Henry to send Brown at the line, then Henry had another crack before the ball was freed to Tuataha on an angled run to dive over.
Kaierau then split Ruapehu wide open with their extra yard of pace as Saurara dashed at the line before the ball was lost and hacked away.
However, Kaierau ran back and their cross kick had a horror bounce for Ruapehu winger Corey Carmichael, with Brosnahan the grateful recipient.
Wanting to keep the tempo up, Kaierau took quick lineouts and charged hard on the outside, with fullback Taylor Kirkwood running to the posts.
A Ruapehu grubber slipped through Saurara's hands and struck his leg and it cost Ruapehu when they held off - as Viliamu ruled no knock-on and the halfback stepped twice and ran right through the green jerseys for the third try in about eight minutes.
Ruapehu hit back from a free kick lineout and pounded the line, then Henry went the blind with Brown pushing him over for 21-12.
Brown linked with Carmichael on another breakaway and although supporting lock Marcus Wallace was dragged down short, the ball came free for Carmichael to reach out and score.
The pace wouldn't let up as Hart cut through twice but couldn't link with his support, then Yarrall and Ethan Robinson nearly broke free, going the other way before the ball went down.
Kaierau got a penalty and Saurara seized his chance with a tap and ran away from all the chasers right on halftime.
Ruapehu first-five George Williams went for a dart at the posts and put Brown over untouched to lock the scores up, yet following sustained Kaierau pressure and a 5m penalty, the fox terrier-like Saurara tapped and scooted low right at the corner, followed by Malo's sideline conversion.
But Ruapehu would not lie down as Hart and Brown forced their way through tackles and the ball went out to flanker Brad Richmond to score out wide, with Evans landing the pressure conversion to tie it back up - the scoreboard attendant having run out of 3s to hang.
Play was intense for the final minutes as it seemed a draw was the likely result, but Saurara would cap his dream match with the winning three-pointer.
-Results: Wanganui Car Centre Kaierau 36 (Anaru Saurara 3, Stu Brosnahan, Taylor Kirkwood tries; Dion Hyland 3 con, Ace Malo con, Saurara pen) bt McCarthy's Transport Ruapehu 33 (Roman Tutauha, Corey Carmichael, Sid Henry, Troy Brown, Brad Richmond tries; Andrew Evans 4 con). HT: 26-19.