The Ford GT40 may have been built to stick it to Ferrari at the 24 Hours of Le Mans, but just over 100 road-going versions were also built for customers. One of the rarest of that breed is about to hit the auction block.

Among the desirable classics at the RM Sotherby's sale taking place during this month's Monterey Car Week will be chassis GT/108, the eighth of 12 GT40 prototypes built and one of just five with the roadster body.

1965 Ford GT40 Roadster prototype (Chassis GT/108)

1965 Ford GT40 Roadster prototype (Chassis GT/108)

Work started on November 2, 1964 at Ford Advanced Vehicles in Slough, United Kingdom, and was completed by March the following year. Being a prototype, many of its components were experimental units so don’t resemble the units on later GT40s. This is especially true for the lights fitted to the car.

GT/108 retains the modified front end used by road-going 1965 GT40 models, as well as the lowered tail section used on roadsters. It also features the same engine it had when it was first sold into private hands, in this case a V-8 with 289 cubic inches of displacement.

1965 Ford GT40 Roadster prototype (Chassis GT/108)

1965 Ford GT40 Roadster prototype (Chassis GT/108)

In addition to its unmolested condition, this car is significant because it was used by Ford and Shelby American for development work. In fact, Carroll Shelby drove Henry Ford II in this very car during a demonstration for Ford's board of directors at the Shelby American facility in Los Angeles back in the 1960s.

Sold by Ford into private hands via Kar Kraft in 1965, chassis GT/108 has been shown at several prestigious events, including past Pebble Beach and Amelia Island Concours d'Elegance events. It's also spent more than two decades in a single owner's collection.

1965 Ford GT40 Roadster prototype (Chassis GT/108)

1965 Ford GT40 Roadster prototype (Chassis GT/108)

If you're keen to bid on this piece of history, RM Sotherby's estimates the final price will between $7 million and $9 million, a range other GT40s have sold for at recent auctions. The sale is booked for August 16.

Despite its rarity, GT40 chassis GT/108 will have to fight for attention at the upcoming Monterey Car Week auctions. Other rare cars going under the hammer include the 1939 Porsche Type 64, a McLaren F1 LM-Specification, and a Niki Lauda Ferrari Formula One car. The full Monterey Car Week event runs the week starting August 11. It concludes on August 18 with the Pebble Beach Concours d'Elegance. For our complete coverage, head to our dedicated hub.