On Sunday at 6 p.m. ET, Darlington Raceway will once again take its place as the happiest place on NASCAR Earth. The hours leading up to the green flag for the 68th running of the Southern 500 have become stock car racing's history lesson and Halloween all at once.

The award-winning NASCAR Throwback has become that rarest of sports phenomenon, a new idea that instantly became a tradition. An idea so successful in its bringing back the past that everyone at the track spends all day sporting face-splitting Richard Petty-like smiles.

The greatest source of that happiness are the race cars themselves, as teams up and down the grid roll out in paint jobs that pay homage to the past. The greatest of those liveries are the ones that instantly connect with the grandstand, colors and numbers that trigger a flood of memories.

However, the process of bringing those designs back to the future isn't as simple as a bunch of guys sitting in the race shop and saying, "What we should do is ... " and then rolling the car into the wrap station. A throwback paint job's path to the racetrack is more winding than any road course, ultimately weaving through dozens of departments and across at least that many desks.

That takes a while. Like, a really long while.

"When did we start the process of deciding what design we would run for this weekend? It was mid-August last year. So, almost a full month before the 2017 Darlington race we were already beginning the process of deciding what we would do for the 2018 Darlington race," Heidi Massey-Bong laughed as she said the words aloud.

She is a senior business advisor at Shell Oil Company and has overseen its NASCAR sponsorships since 2007. That started with Richard Childress Racing. These days, she works with Penske Racing and Joey Logano. On Sunday, Logano's No. 22 Ford will be wrapped in its familiar Pennzoil colors (yes, Pennzoil is a Shell brand, more on that later), but those colors will be presented via a design that made its debut 20 years ago this season but hasn't been on the track in a Cup series event in more than a decade.

It's the yellow-and-black door-striped paint job made famous by Steve Park, who in 1998 became the first full-time Cup series driver for Dale Earnhardt Inc., ultimately steering his No. 1 Pennzoil Chevy to two wins over a little more than five seasons.

The conversation about bringing back that look for NASCAR Throwback actually started with Park himself, who was approached during the 2017 PGA Championship in Charlotte, North Carolina, by Sam Brown, a longtime motorsports marketing and PR executive who works for Shell's U.S. Motorsports agency, Sport Dimensions Inc. Brown and Massey-Bong knew the 20th anniversary of Park and DEI's Pennzoil debut was coming up, so it felt like a natural fit.

"I was all for it from the beginning," said Park, who has run an homage to that paint job (unofficial and not Pennzoil sponsored) himself in lower level races. "But I also wanted to make sure it was actually going to happen before I let myself get too excited. I knew that it was going to take a lot of people from a lot of different places to sign off on it to make that happen."

Massey-Bong was fully aware of that obstacle course. She lives that labor on a daily basis but also describes it as a labor of love. Especially when it came to this particular paint scheme. Over the previous three years of Darlington's NASCAR Throwback concept, she is willing to concede that Shell's decisions have included hits and misses. But no matter what idea they rolled out, the response from fans was the same.

"They always came back with, 'When are you going to run the Steve Park car?!'" she said. "In fact, we got that question not only when we revealed what we were doing on Darlington weekend. We get it year round. We are very fortunate that after decades of racing history, we have so many options to choose from. So many legendary cars. So many great moments. So many anniversaries that come with those. But sometimes it's just obvious. This one was obvious and the fans were the ones who reminded us of that. A lot."

A few weeks after Logano finished 18th in his Shell-Pennzoil tribute to Jimmy Vasser's 2002 IndyCar ride (15th anniversary), Massey-Bong started shopping the idea within her Houston offices. As with any massive corporate entity, there are no straight lines from Point A to Point B, let alone Point Z.

For starters, the sponsorship of Logano's car is a carefully constructed calendar grid of Shell vs. Pennzoil, depending on markets, product launches and the like. Then there are strict marketing rules that must be adhered to within those plans. For example, initially there was a lot of internal pushback to the idea of including so much black into the Park paint job. While black in 1998 was cool, Pennzoil's current corporate palate tries to avoid the color whenever possible.

And perhaps the biggest hurdle of them all is certainly not a problem unique to Shell.

Joey Logano, left, and Steve Park pose in front of Logano's Darlington throwback car. Courtesy of Clutch Studios

"Selling retro and tribute to young people who weren't around when these moments took place and iconic race cars were on the track, that can be a challenge," Massey-Bong explained. "This is an amazing company that is so future-focused, pushing new science and technology, and here I come, saying, 'Hey! Let's talk about what this place looked like 20 years ago!' But I see that as a chance to educate. I get to tell people a story, and ultimately that's what a project like this is about -- a paint scheme that tells a story."

With internal notes in hand, Massey-Bong and Brown went to Charlotte designer Steve Breakfield. Breakfield, with images of Park's '98 ride available, took the first crack at making those lines and colors -- designed for the bulletlike '98 Chevy Monte Carlo -- to fit today's taller, more angular Ford Fusion.

"You know who came up with that original design, right?" Park said. "Dale Earnhardt. So, no pressure, right?"

While Breakfield's initial ideas bounced back and forth with Shell HQ, who made tweaks accordingly, meetings were taking place to determine when those drawings would be placed in front of one of the few motorsports figures as intimidating as The Intimidator.

"Before we took anything to Roger Penske, our first meetings to talk about this idea specifically were in January 2018," said Jonathan Gibson, Penske Racing vice president of marketing and communications. "Those meetings are about story. What's the story here? And obviously, Steve Park's story is a great one that connects with fans.

"Then you talk authenticity. Those fans deserve that we roll out a car that's as authentic as possible. If you know anything about Roger Penske, then you know that he demands that, as well. And his knowledge of the history of the sport is so deep, he knows in an instant if something isn't authentic."

By early spring, Penske had the design and, yes, he had some notes. as well. So ... it went back to Breakfield. Then it went back to Penske. Then it went back to Breakfield. In the end, there were about 20 versions of the paint scheme before it finally received the rubber stamp of approval.

And during all of this, both the race team and Shell were in constant communication with Darlington Raceway and NASCAR. Why? To ensure Logano's car didn't too closely resemble another team's throwback plans and to make sure their announcement was on a calendar spot that would provide maximum marketing impact.

"What you don't want to do is unveil your car the same day that two other teams are unveiling theirs," Gibson explained. "In 2015 (the first NASCAR Throwback event), a lot of days got overwhelming with all the announcements. It's only fair to our corporate partners, our fans and the fans of Steve Park that they really get to enjoy a really fun moment."

A big part of preserving that enjoyment is secrecy, keeping the newly wrapped car under wraps until the big day has arrived. At Penske Racing headquarters in Mooresville, North Carolina, that's hard to do. The massive race shop is open for all to see, thanks to a "fan view" walkway that anyone off the street can stroll for free. And Tweet for free.

"We had a show car wrapped in the new design and then it was like, well, we can't just park in the shop until the unveiling. It will be a secret for like 10 seconds." Gibson said, recalling a few incidents where fans unwittingly spilled Penske secrets via social media. "So Joey agreed to hide it in his shop. He's got a really nice studio he's built that's not open to the world like we are, so we stuck it in there for a little while."

Finally, on July 31, Logano yanked the cover off that show car, carried on live TV. Standing beside him was a beaming Park. On Sunday at Darlington, they will be standing side-by-side again, this time alongside the actual race car, about to roll out at the racetrack where, in 2001, Park suffered an accident that many feared would end his career. Instead, he came back to run that Pennzoil machine for another season and a half.

Now Park is coming back again, thanks to more than a year's worth of behind-the-scenes work.

"I am a New England racing guy, and Steve is a New England racing guy, and when I was 8 years old, he was driving this car," Logano said. "A lot of people worked hard to make this happen. Now I just hope that I can make them -- and Steve -- proud."