The Ford Cosworth RS500 was built in 1986 and has just 9,180 miles on the clock.
It sold for a figure “very close” to the £350,000 asking price at a KGF Classic Cars auction in Peterborough last month.
A spokesman said the buyer was a Brit – adding both they and the seller are “very happy”.
The figure is the second-highest sum paid for a Cosworth at auction, after one sold for £596,520 last year.
Only 52 “Cossies” were ever made in the moonstone blue colour sported by the car sold in Peterborough.
The Cosworth got its RS500 tag from the fact that just five hundred models were produced in the late 1980s.
As well as the 52 moonstone blue, there were 56 diamond white – all the rest were black.
Millions watched Cosworths sweep all before them in the British Touring Car Championship at Brands Hatch and Silverstone.
The one auctioned last year for a jaw-dropping £596,000 went to a multi-millionaire fan living in Dubai.
The Cossie sold by KGF Classic Cars was one of the 30 ‘road legal’ cars kept back for the public to buy and has never been raced.
KGF Classic Cars said: “This car was built December 1986 at the Genk assembly plant in Germany.
“The vehicle was dispatched on the 5th August 1987 to its one and only custodian, Mr McIntosh.
“The new vehicle sales invoice reveals a price paid of £20,249.55 with a subsequent invoice for £332.48 for a Ford remote alarm.
“Mr McIntosh was a fastidious owner retaining every document from Ford recall letters to regular service invoices and MOT certificates.
“Not one for public displays or shows, the vehicle was rarely seen out of his property.
“A major service and cambelt change along with all fluids have been changed making the car A1 mechanically.
“It is ready for immediate enjoyment should the next lucky owner wish.”
The RS500s were not just any old Ford – they were turbo-powered rockets capable of more than 150mph.
They had an extra rear spoiler under the huge whale-tail wing, a front bumper and badges on rear tailgate and front wings.