When a concept car’s time in the spotlight is done, its manufacturer typically adopts its design for production, or ushers it off the show stand and into storage…or the scrapyard.

The Dual-Ghia Convertible is the result of an unlikely third outcome: A case where a visionary entrepreneur picked up a concept discarded by a major automaker and put it into production independently.

After Dodge decided not to pursue its striking, Ghia-bodied Firearrow concepts, Eugene Casaroll—owner of a Detroit-based new car-shipping company, proprietor of specialty vehicle manufacturer Dual-Motors, and an Indianapolis 500 car sponsor—acquired the rights to the design.

In 1955, he unveiled an evolution of the Firearrow IV, which he dubbed the Firebomb.

The production car that arrived the following year lost none of the Firebomb’s appeal, nor its winning combination of a Dodge chassis and V-8 running gear topped by Carrozzeria Ghia-crafted coachwork, but it gained a somewhat more prosaic name: The Dual-...