NEW YORK (CNN/Money) - With a new, redesigned Mustang due to start production in the fall, supplies of the current version are expected to dry up this summer as demand outstrips expectations, a Ford Motor Co. spokesman said Thursday.

2004 Ford SVT Mustang Cobra

The spokesman, Wes Sherwood, said the automaker expects supplies of the popular pony car to run out before it can launch the new, redesigned 2005 version. Mustang sales are up 16 percent so far this year, surpassing Ford's expectations.

Ford's legendary Rouge plant in Dearborn, Mich. has been cranking out Mustangs on overtime to keep inventory filled, according to industry publication Automotive News.

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Mustang production at Dearborn will end May 10, the Ford (F: up $0.93 to $15.87, Research, Estimates) spokesman said. The new Mustang will be produced in the fall -- Ford won't give a more specific date -- in a Flat Rock, Mich., plant operated in a joint venture with Mazda.

Thanks to the overtime production effort, Mustang supplies had been high through the winter months, when Mustang sales usually slack off. This past January, sales were 47 percent higher than last January.

Sales for the rear-wheel drive Mustang are usually strongest in spring and summer, and now inventories are dropping fast, Sherwood said. Automotive News reported that, on April 1, Ford had a 96-day supply of Mustangs on hand, down from a 127-day supply one month before.

The car's unique place in automotive history is probably driving some of the current demand, according to the spokesman. Not only is this the last Mustang to be produced at the Rouge plant, but all Mustangs this year sport special 40th Anniversary badging.

"For the Mustang enthusiasts out there, this is going to be a really collectible car," said Sherwood.

The current $3,000 rebate on 2004 Mustangs is expected to continue.

"We feel that the incentive is at the right place right now to keep sales brisk," said Ford spokesman Miles Johnson.

Those who want a convertible Mustang will have to act fast or they could be in for a long wait. After the current stock of convertibles run out, buyers will have to wait until spring 2005 before a convertible version of the new design becomes available.