The Torana set to become the most expensive Holden ever

An Australian Touring Car Championship-winning Torana that's approaching its 40th birthday could go down as one of the most expensive Holden in history, with an estimated price tag of up to $1 million in an auction of some of the world's rarest and most sought-after cars.

The centrepiece of an upcoming auction by Mossgreen's, the number 7 Torana A9X – still in its racing livery complete with roll cage and stone chips – beat Peter Brock in the 1979 touring car championship, at the time a monumental feat against the might of the Holden Dealer Team.

An Aussie icon

James Nicholls, the man behind the auction which takes place in Sydney on May 28, describes the green, white and blue V8-powered hatch as "a very rare and unusual car and it's a particularly special car in that it's completely original".

"We feel this car is probably the most exciting Australian race car to come on to the Australian market…it's a very, very special car," says Nicholls.

Despite the hoped-for anticipated big buck price tag, the Torana is not expected to be the most expensive car at the multi-million dollar auction.

Money on wheels

That honour goes to an Aston Martin DB5 – the same type made famous in early James Bond movies – with a price estimate up to $1.6 million.

Describing Aston Martins as "international currency" Nicholls says there has been some interest overseas for the likes of the DB5, something not unusual in the world of collectible cars.

Fixer-upper

For those keen to get their hands dirty there's an almighty restoration program in the form of a 1953 Alvis-Healey Three Litre Sports Convertible.

One of only 25 built, the car spent much of its life in the US before being left to decay to the point where it is now rusted and falling apart.

"You're going to need broad shoulders to take that project on," says Nicholls, acknowledging it is a "complete wreck".

Ticking boxes

However, he says the rarity and provenance of the car could fetch it up to $40,000.

"The wonderful thing about that car is that it's all there, it's all original … all the bits and pieces are there, pretty much…"

While it may look ready for the scrapheap, Nicholls says its originality – something increasingly important with car collectors – is near-perfect.

"The driving points [for collectible cars] are rarity, desirability, originality, condition, history and provenance," he says. "The more of those six boxes you can tick the more your car is potentially worth."

Number 36

In terms of price per kilogram, though, look no further than a NSW numberplate displaying "36". The price estimate is between $400,000 and $450,000.

At the other end of the scale is a comparative bargain, a 1913 Ford Model T, expected to get as much as $38,000.

Check out the gallery above to see a selection of the best collectible cars up for grabs.