Significant ACs are the stuff of Jim Feldman’s collection, but perhaps none is more significant than this Ford Zephyr-powered 1963 Ace Roadster.

It is the model, and revised body, that led directly to the Shelby Cobra—the chrysalis from which the Cobra as we know it eventually emerged.

Introduced in 1953, the AC Ace roadster and its closed Aceca coupe sibling were based on a chassis design by John Tojeiro, with four-wheel independent suspension and transverse leaf springs.

The sleek body was inspired by early Ferrari barchettas.

The engine availability tribulations that emerged as production progressed—ultimately fostering AC’s positive response to Carroll Shelby’s inquiries—are well known, as both AC’s own 2-liter six and the Bristol 2-liter ended production in the late 1950s.

AC cast about for a replacement, of which the best known is the thinwall-casting small Ford V-8 that powered the Cobra.

But AC also produced a limited series of Ace Roadsters powered by Ford of England’s 2...