The three drivers -- who filled the podium in the 2007 Leinster Trophy at Mondello Park -- are all now making their mark in US racing.
Dempsey's debut podium finish in the Indy Lights Championship behind Conor Daly came after a last-minute deal with O2 Racing Technology and will help secure his tenure with the squad beyond his initial four-race contract.
Having belied his lack of testing by qualifying a strong fifth, Dempsey made a stunning getaway and played his hand decisively to lead on lap one.
A lack of test miles showed as the handling on his car deteriorated and he dropped back to third behind Daly.
Nonetheless, Dempsey was delighted with the result.
"Considering we didn't have anything on the table a few weeks before the race, I'm delighted with a debut podium," says the former double Dunlop Racing Driver of the Year. We were competitive right from the start of practice and we could have been further up the grid if I hadn't missed the last 15 minutes of qualifying after damaging the car against the wall.
"I told the team I'd make up for that and I just made sure I got my apex at turn one and got on the power early to drag past the others on the run to turn two."
His deal with the team runs until after the fourth round of the series at Indianapolis in May, but his form has delighted new sponsor Microbiology International and he is confident it will be extended.
Reigning Dunlop Driver of the Year McKenna produced the best performance by a Star Mazda series debutant as he qualified and finished fourth for GDT Motorsport.
McKenna was also making up for a deficit in pre-season test mileage compared to his rivals, but was right on the pace in the third rung of the ladder to Indy car racing.
After slipping behind last year's USF2000 title rival Sage Karam, McKenna battled his way back into fourth as his fellow rookie retired, triggering another full-course yellow.
In finishing fourth, McKenna fulfilled his pre-race goals and justified GDT Motorsport's faith.
"That was a tough weekend and it's great to be able to reward the team with a strong result right from the start," he said.
"The build-up to the weekend was pretty hectic as we tried to pack as much as we could into a short private test and the official test at Barber the week before."
Meanwhile, Boyd's US racing rookie season improved in St Petersburg as the Antrim racer finished third in the second race of the weekend, the fourth race of the series.
He is now fifth in the points standings.