The $150,000 Northern Rivers feature had to be staged at Grafton when rain late in the week made it impossible for Lismore to host the race.
While Dunn had five runners in the race the Murwillumbah trainer wasn't surprised it took two horses he described as "big and tough" to get the job done.
Tribeca Star ($3.80 favourite) was brilliantly ridden by Matthew McGuren, who rode five winners at the meeting, finding the fence midfield before working his way into the clear and holding off the challenge of Rainbow Connection ($5) just ahead of David Mccolm's Fairway Choice ($4.80).
It was Tribeca Star's seventh run for a preparation that started in late September.
"He's done a wonderful job, he's been up a long time,'' Dunn said.
"He's clocked plenty of miles on the Highway, that's for sure, he's been up and down the coast three times. It was great to see him do that.
"He was the horse we set for this a very long time ago. The team's done a wonderful job to keep him in such good order for such a long period of time.
"Rainbow Connection didn't get as soft a run as Tribeca Star and to get the two through was exactly what we were looking for."
Dunn won the 2020 Newhaven Park Country Championships Final with Gracie Belle and 2024 is his first year back in the series after a couple of years with a Sydney base.
It was his fourth win in the Northern Rivers regional final following La Scopa (2019), Snitz (2018) and Perfect Dare (2017).
He said with the Final not until April 6 it's likely both horses will need to race again to keep them up to the mark for what will be a tougher test.
"They've both had lots of racing and seasoning, they are big strong horses and that goes a long way in high pressure races and that's what Randwick is going to be,'' he said.
McGuren couldn't have planned the race out any better after he was able to ease Tribeca Star into a spot behind stablemate Emperor and enjoy an economical run.
"It kept unfolding how I wanted it and he was too good,'' McGuren said.
"I probably got there too soon, he got there and put them (away) but late he found the 1400m just out.
"The way the runs unfolded for me I had to take them to get to the best part of the track.
"Randwick is probably a bit harder, I said to connections it wouldn't hurt to be ridden a touch softer and a bit more patient. "
The win, and qualification for the Final that comes with it, saw Tribeca Star vault into favouritism at $6 with TAB for the Final with Rainbow Connection an $11 chance.
