The 1966 GT350 Convertibles: Why There Were Four, Not Six

The full lineage of the street cars, race cars and rental cars is in our history of Shelby's Mustangs. This piece stays with the open cars of 1966: how many there really were, what made them different, and why the count changed.

Six or four: how many 1966 Shelby GT350 convertibles were built

The hobby believed for a long time that Shelby American built six convertibles in 1966. That figure got repeated so often it hardened into fact. The documents say four.

The proof turned up in 1987, in Shelby's office in Gardena, California. Among the papers was a shop order dated June 7, 1966, which reads: "Four experimental convertibles are being run through the shop at present time." Not six. Four. Once that order surfaced, the two extra cars in the story had nowhere to live, because there was no paper behind them and no serial numbers to point to. The researchers who went through those files did what good registrars do: they let the document overrule the legend.

Where the number six came from in the first place, I cannot tell you with any confidence, and I would rather say so than invent an origin. What I can tell you is that a 1966 Mustang convertible and a set of stripes are not hard to come by, and in a hobby where a real one is worth a great deal, look-alikes were always going to exist. Every one of those helps a myth along.

The June 1966 order and what "experimental" meant

Look at the date first. June 7, 1966, is late in a model year. By then Shelby American had already built the bulk of a year that came to 2,378 cars, including about 1,370 regular GT350 fastbacks for the public and roughly 1,000 cars for Hertz. A convertible was never on the 1966 order form a buyer could walk in and fill out. It was a short, late run on the side.

Then read the next line, because it tells you what "experimental" meant. One of the four was already sold, and the other three "will be used for test purposes in anticipation of a 1967½ GT350 convertible." So these were test cars for an open Shelby that Shelby American was planning, not a production model already on sale. Shelby's 1966 GT350 was a fastback car, and its whole identity, from the rear quarter windows to the brake scoops, was built around that roof. Building it without that roof raised obvious questions about how the car looked, how it was trimmed and whether anybody would pay for it. Four cars was a small, cheap way to find out.

The order gives the what and the why in one sentence. What exactly Shelby's people were worried about is my reading, not a quote from Shelby American, and I want to keep the two apart. You are welcome to argue with it at the next meet.

What made the four different from the fastbacks

Underneath, these were 1966 GT350s, with the same 289 rated at 306 hp. What set them apart is a list of details you would never find on the regular cars, and almost all of it comes from the description of one of the four offered at auction in 2020.

Start with the colors: Ivy Green, Candyapple Red, Sapphire Blue and Springtime Yellow, one car in each. The Ivy Green car is 6S2375, the yellow one is 6S2376 and the red one is 6S2377. None of them was Wimbledon White, which is a nice irony for a model whose first year had been white-only. Two had automatic transmissions and two had four-speeds: the green car is an automatic, the yellow and red cars are four-speeds, which leaves the blue car with the other automatic. All four had factory air conditioning, which the auction description says makes them the only Shelbys of 1965 and 1966 to leave with factory air. On a car whose fastback brothers wore working scoops to cool the rear brakes, the quarter scoops on the convertibles were made non-functional so the top could fold.

Even with air and a folding top, the convertibles were not the rarest thing Shelby did to a 1966 car. About 11 GT350s got the factory supercharger that year, and the Paxton option cost $670 on top of the car. Four convertibles and a handful of blown fastbacks: that is the whole list of 1966 oddities most people can name.

6S2375 and the paper trail of one car

The best way to see how a myth gets corrected is to follow one car. Serial 6S2375 is the earliest of the four by number, and it is the Ivy Green car. It spent about eight months as a Shelby American test car, went to Shelby's Hi-Performance Motors in El Segundo, and was shipped to Hayward Ford on February 14, 1967, well into the next model year. It was offered at Mecum's Indianapolis auction in 2020, and its sale description is where most of the published detail on the four comes from.

The car that matches the "one of these units is sold" line in the order is most likely 6S2377, the red four-speed. Its first owner was Bob Shane of the Kingston Trio, who picked it up at S&C Motors in San Francisco on July 7, 1966, a month after the order was written.

I will say plainly that auction copy is written to sell a car. That is not a reason to throw it out, but it is a reason to check it against the club records, and the Shelby American Automobile Club registry is the place those records live. I did what I could from the outside. SAAC members working from the registry confirm the yellow car as a four-speed with factory air that went to Hi-Performance Motors in 1966, and the sale listing for the red car cites SAAC research for the count of four. Wikipedia's Shelby history also describes four experimental convertibles built for testing ahead of a 1967½ convertible. The club was founded in 1975 by a handful of owners, and its registry was pieced together from serial numbers and owner records over decades. A 1997 edition of the registry drew on documents loaned from Shelby's own files. That is the kind of record that ends a six-versus-four argument for good.

"I heard about the six convertibles for years from men I trusted. Then somebody pulled an order out of an old filing cabinet and it said four, and that was the end of it. Nobody lost face. We just got a better story."

Wayne Coburn

From four experiments to a catalog convertible

The experiment did not lead straight to a production car. For 1967 Shelby built exactly one GT500 convertible, car 0139, so the open Shelby stayed a one-off for another year.

The real answer came for 1968. That year Shelby offered convertibles as a regular model, and buyers took 404 GT350 convertibles, 402 GT500 convertibles and about 517 GT500KR convertibles. In two model years the open Shelby went from four cars on an experimental order to well over a thousand. Read that way, the 1966 convertibles were the first draft.

That is also why the count matters more than it seems. Four cars is a story about a small company testing an idea late in a busy year. Six cars would have been a story with two missing chapters and nobody able to produce them. The paperwork gave us the shorter, truer version, and the hobby is better for having the document in hand instead of the legend.

Sources and notes

• 1 of 4 1966 Shelby GT350 convertibles built, Mecum Indy 2020 (duPont Registry, sponsored auction copy)
• Very first of four 1966 Shelby GT350 convertibles up for bids (Motorious)
• SAAC forum thread on the 1966 convertibles, 6S2376 and 6S2378
• 1966 Shelby GT350 convertible 6S2377 sale listing (ClassicCars.com)
• Shelby Mustang (Wikipedia)
• Shelby FAQ and production list (archived)