(CNN Money) -- Old pickup trucks aren't just old trucks anymore. They are, officially, collectible.
Classic pickups are becoming a favorite item at collector auctions. For example, auction prices for 1947 to '55 Chevrolet 3100 pickups have risen 33% in the last three years, according to the collector car market watchers at Hagerty Insurance. Prices for newer 1973 to '87 GMC trucks have risen 22%, and prices for big 1945 to 68 Dodge Power Wagons have gone up 34%.
At January's Arizona collector car auctions -- events that are held annually by several different auction companies -- the most expensive pickups sold were heavily modified and modernized. The most expensive one of all was a highly customized 1941 Dodge Power Wagon with raised suspension and a Brazilian hardwood bed. It was sold by Barrett-Jackson for $220,000. The most expensive restored, but not otherwise modified truck was a 1947 Power Wagon sold by the Russo and Steele auction house for $115,000.
Those are of course not your usual retired hay haulers. Buyers got very nicely restored trucks for $30,000 to $40,000 at those same auctions. Values are rising as car collectors begin to see trucks as affordable pieces of drivable Americana.
Thanks to careful restoration, some of these trucks look just as good as they did the day they left the factory. Pickups' simple, rugged engineering makes that level of finish easier to achieve on a truck than on a car.
"They're so easy to work on," said McKeel Hagerty, head of Hagerty Insurance. "The ability to really create an almost [competition]-level restoration on one of these is a lot cheaper than doing it on a Maserati."
Truck restorers can easily find new or unused versions of the parts their truck originally had. And a number of companies make modern parts, such as power steering gear and disc brakes, that fit old trucks. These parts make old trucks drive more like modern ones. And collectors are accepting of modifications, especially if the changes are made in a way that allows them to be changed back later.
But trucks don't have to be pristine to find an audience. B. Mitchell Carlson, who writes about the collector car market, owns several older cars including a 1947 International Harvester pickup that he uses for hauling but still takes to car shows. The paint is pretty faded, but that's just fine with him.
"That doesn't bother me and it doesn't bother a lot of guys and gals that are into trucks," he said.
The increasing popularity of pickups is tied into another big trend in collector cars; the popularity of vintage SUVs such as Ford Broncos and Chevy Blazers, said John Kraman who provides collector car commentary for Mecum Auctions' TV broadcasts. "They fall into that truck category."
Older Land Rovers, Jeep Grand Wagoneers and Toyota Land Cruisers are also increasingly valuable. Pickups, which are simpler and were manufactured in much larger numbers, provide an easier and more affordable way to enjoy the cool image of a classic truck.
Given the hard work to which most old trucks have been subjected, a nicely restored one is particularly eye-catching.
Owners are taking the time to ensure the quality of the body work so the trucks look really beautiful, said Craig Jackson, president of the Barrett-Jackson auction company. "It just happens to be they have a bed in the back rather than two small seats like a muscle car," he said.
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