HARPSWELL — There are only about half a dozen auto body shops in the country that specialize in the service and restoration of the iconic Volkswagen van, and one of them is off a dirt road in Harpswell.

It’s hard to find, and so is a man who stops there frequently: Bob Muller, who runs Vintage Van Adventures, a business that rents restored Westphalia-model camper vans to vacationers looking to explore Maine on four wheels.

“This is about the experience,” Muller said in a recent interview. “This isn’t your fast-food rent-a-car.”

Muller, 66, built his four-vehicle fleet with the help of mechanic Jon Gagnon, whose Foreign Auto Supply has been restoring Volkswagen vans and buses for 25 years, with clients as far away as California.

Like Gagnon, Muller is sought out by people with a niche interest — those, Muller said, who like “the easiness, the compactness” of the vans, which can sleep four people and house kitchens in their mid-sized cabins.

“(They’re) called the Swiss Army knife of vans,” he said.

Muller, a geographic surveyor by day, has loved cars ever since he restored a 1959 VW Karmann Ghia when he was 15 years old.

He turned his hobby into a rental business three years ago. A little before that, Muller had been looking to buy a car for his daughter, who was headed to college.

He bought her a van, a purchase that led him to Gagnon; when it wasn’t restored in time for Muller’s daughter to use, Muller had a different idea for it.

Gagnon has since restored four camper vans — which Volkswagen stopped making in 1991 — for Muller at his Harpswell shop, where he and his crew of five mechanics work on as many as 60 vans a year for clients around the country and abroad.

Muller’s 30-year-old vans, available to rent for a flat fee of $1,675 a week, “are totally provisioned,” Muller said. “There isn’t a thing you should need except your toiletries, your wine and your cheese.”

He only rents them for a week at a time, usually during July and August, to keep them from being driven too far from Maine, where Muller would like his clients to stay.

“I’m marketing the experience, not the van,” Muller said, adding that he surprises his clients with a gift basket of Maine-made treats including jams and syrups.

Thanks to a rising interest in vintage camper vans, he said, his rental business has grown every year since he started.

Muller was speaking from the driver’s seat of Goldie, a tan model from the mid-’80s, last Friday afternoon; a trio of yellow flowers sprouted from holes punched in the dash.

All four of his vans have names — Bono, because U2 is featured on the license plate — and Lilee, after the former Brunswick restaurant where Muller’s daughter worked.

They have personalities, too.

“You drive her like any other car,” Muller assured, but in order to turn onto Mountain Road, he had to rotate Goldie’s enormous steering wheel, the size and shape of a pizza pan.

Muller was headed to Gagnon’s shop in Harpswell center, where mechanics were working on several ongoing projects: engine conversions, services and repairs.

Muller said he relies on the expertise at Gagnon’s to ensure his rentals are safe. But he said the average repair shop can fix any glitches his customers may encounter on the road.

“This thing is new in the lungs, the heart and the veins,” Muller said of Goldie.

He said a full-scale restoration can easily cost more than $40,000 just to cover the basic costs of the engine, paint and labor.

Around 2 p.m. Friday, Gagnon had not yet had lunch. He was still upstairs in his cave-like office, revising a self-authored manual he provides to clients: a customized guide to how to operate and maintain the restored vehicles, which combine modern technology with vintage hardware.

A cardiac surgeon once compared himself to Gagnon, the mechanic said, who explained how he retrofits new, German engines to fit into the antique vans using custom parts.

It’s work that Gagnon, a humble ex-hockey player in his mid-40s, learned under the tutelage of several mechanic “gurus,” but requires constant innovation.

“What’s different about what we do is, we keep pushing ourselves to make changes, and pushing the technology,” he said. That can include anything from installing solar panels so the van can drive “off the grid,” to painting a Grateful Dead skull on the iconic body.

Whatever the client’s request is, “we’re bridging the gap” between old and new, Gagnon said. His restorations always seek to make the old vehicles simpler and better, with improved fuel efficiency and horsepower, and fewer emissions.

His bone yard of van carcasses is hardly visible from the residential dirt road where his shop is off Doughty’s Point Road. And likewise, the business is almost unknown locally.

“We’re known much better in Huntington Beach (California)” Gagnon said, “than a mile from here.”

A Volkswagen van sits on a lift during restoration at Foreign Auto Supply in Harpswell while a mechanic talks with Bob Muller, right, who rents the classic vehicles to vacationers in the summer.

Goldie is a 1985 Volkswagen Westphalia camper van, at Foreign Auto Supply in Harpswell. Goldie belongs to Bob Muller, who rents her for a week at a time to vacationers over the summer.