It was classic Carroll Shelby, a delightfully mad idea made even madder: Take the already ferocious 289 Cobra .

.

.

and “upgrade” it with a 427-cubic-inch V-8.

Though Shelby intended to race the 427 Cobra, by the time FIA inspectors arrived at his facility, only 51 of the cars had been completed, and so he was adamantly denied their homologation approval.

Shelby consequently painted and completed 29 competition chassis with fully trimmed interiors, and shrewdly marketed them as the 427 S/C or “Semi-Competition,” the fastest roadgoing car ever built—while retaining the oil cooler, riveted hood scoop, flared fenders, side exhausts, dual lightweight batteries, 42-gallon fuel tank, and external fuel filler of full “competition” models.

Just as Jaguar’s XKSS was a thinly veiled D-Type racecar, so too was the 427 S/C Cobra a barely disguised, roadgoing variant of the 427 Competition Cobra.

They were insanely, brutally quick, faster than many full-bore racing cars of the period, and ca...