Regan Smith was quick to accept an offer to race in the Daytona 500 as Kurt Busch's replacement driver.

He did have one slight concern, though, about spending an additional day in Florida. His pregnant wife, Megan, was at home in North Carolina expecting their first child. But he said the couple agreed in advance that should she go into labor, he should complete his races before heading home.

"I've asked her to keep her legs crossed as long as she can if she does go into labor," Smith joked at Daytona International Speedway last weekend.

Everything worked out just fine for the Smiths, who welcomed son Rhett Lee on Wednesday, an off day for NASCAR drivers.

The baby had a short window to arrive: Smith gets back on track Thursday at Atlanta Motor Speedway, where he'll drive Busch's car for Stewart-Haas Racing in an open NASCAR test. He's slated to fill his regular role as Xfinity Series driver for JR Motorsports all weekend, and do double-duty in the Sprint Cup Series for SHR. Busch has been indefinitely suspended by NASCAR.

Smith, who ran four full seasons in the Cup series from 2008 through 2012, has spent the last two as a full-time driver for JR Motorsports in NASCAR's second-tier series. But he has been a super substitute a handful of times the last few years.

Smith filled in unexpectedly for Dale Earnhardt Jr. in 2012 when Earnhardt was sidelined with a concussion, and he flew in on race day last year at Watkins Glen when SHR needed an emergency substitute for Tony Stewart.

Now he's making his second start for Busch, who was suspended Friday. But with 173 career Cup starts, Smith thinks he's capable of moving car-to-car and stepping in wherever needed.

"I think the fortunate thing is that I've done enough Cup races to where I'm familiar with most of the cars," he said. "They all take their own kind of shape and form. You make the most of them. I don't think anybody wants to be in the scenario where you have to sub under circumstances, whatever they may be.

"And with that said, if it happens, you want to make the most of that opportunity."

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KYLE BUSCH-FUTURE RACING: Kyle Busch is back in North Carolina receiving treatment on his broken right leg and broken left foot, and it's not clear how long he'll be sidelined.

But when he does return to racing, it's unlikely that team owner Joe Gibbs will limit his racing outside the Sprint Cup Series. Busch was injured Saturday in the season-opening Xfinity Series race at Daytona, a day before the Daytona 500.

Gibbs said it's hard to hold Busch back because aside from his wife, Samantha, racing is all he has. Busch owns a NASCAR Truck Series team at Kyle Busch Motorsports.

"Let's think about it for a minute, he has his own race team, loves that, wants to race it, it's a big part of him and Sam and his future," Gibbs said. "So you kind of think about that and you know he's going to be racing some trucks. He has Sam and he has racing. He loves it."

JGR tried to cut Busch's schedule in 2012, when he ran just three Truck Series races and 22 events in Xfinity. The reduction in races made him miserable and he had one of the worst seasons of his career: He won one race, missed the Chase, and went winless in Xfinity and Trucks.

"At one point there in his career, we did cut back quite a bit and it was one of the tougher years," Gibbs said. "I felt like in his case, he just loves it so much and felt like it was something that really makes his happy, keeps him excited about life and you always wrestle with that."

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BOWYER-FOX ANALYST: Clint Bowyer is the latest driver to be added to the Fox and Fox Sports 1 coverage of the Xfinity Series.

Bowyer will be the analyst alongside Adam Alexander and Michael Waltrip for next month's race at Fontana, California, and the May race at Charlotte Motor Speedway.

Bowyer is the fifth Sprint Cup Series driver to be added to the rotation. Kevin Harvick was in the booth for last week's season-opener, and Jeff Gordon, Brad Keselowski and Danica Patrick also have upcoming races scheduled.

Harvick said he enjoyed his time in the booth more than he expected.

"I felt like you bring that perspective to the booth of right off the race track and being able to really relate to what's going on out of the race track," he said. "It is something I definitely enjoyed and had a lot of fun doing."

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BIG BILL: A new book about NASCAR founder Bill France Sr. will be released next week, and it marks the first official biography of the man who organized stock car racing.

"Big Bill: The Life and Times of NASCAR Founder Bill France Sr.," will be released March 3 by Random House. It's written by H.A. "Herb" Branham, a former journalist and NASCAR public relations executive who now runs the International Speedway Corporation's Archives and Research Center in Daytona Beach, Florida.

Branham said he had unfettered access to write the book, with no interference from the France family. He'd already written "Bill France Jr.: The Man who Made NASCAR," so there was no apprehension about Branham's 357-page prequel.

Using a conversational style, Branham tells the story of France's creation of NASCAR as a way to incorporate stock car racing in late 1947. He built Daytona International Speedway and Talladega Superspeedway, and ruled as a dictator.

Branham said he enjoyed the interviews he conducted as part of the book, particularly a lengthy sit-down with A.J. Foyt, who grew emotional discussing France.

"I didn't really see that coming, but A.J. had a reverence for Bill France, felt like he'd been a father-figure to A.J., and really credited him for much of what he accomplished in his career," Branham said.