Indy IROC: Johnson's race, Busch's crown

"I just dreamed about this day, and it came true," Busch said. "It's an honour to drive in this series, to compete against the best of the best and beat them."

For Busch, an IROC rookie, a fourth-place finish was enough to clinch the title and keep his NASCAR Winston Cup team-mate, Mark Martin, from making IROC history.

Martin was attempting to break Dale Earnhardt's IROC records for championships and career wins. However, Mark finished fifth and remains tied with Earnhardt with four IROC championships. Earnhardt, Martin and Al Unser Jr. share the record for most IROC wins with 11.

Martin also was chasing his fourth consecutive IROC win at IMS, but he couldn't make up any ground on Busch after the field got strung out over the 2.5-mile oval.

"I need to thank my Winston Cup crew and Mark Martin," Busch said. "He was a true competitor until the end."

As Busch was winning his points battle, Johnson was winning the race. He passed Castroneves on a restart on the 21st lap, then held off Kevin Harvick and Ryan Newman to post his first IROC win.

"Hopefully this is the sign of good things to come," said Johnson, who will start sixth Sunday in the Brickyard 400 at IMS.

As Johnson passed Castroneves, the two-time Indianapolis 500 winner, on the restart after the two cars were side-by-side for a lap, the pro-NASCAR crowd roared its approval.

"I didn't think I'd have anything for him," Johnson said. "When the caution came out, I knew I would have about a lap to get something done. I knew it was going to be my only opportunity."