A similar design that used the powertrain from the Autobianchi Primula was done by Dante Giacosa at Società industriale ricerche automobilistiche (SIRA - Automotive Industry Research Company), with initial fabrication done by OSI, and a full prototype called the G31 built later by Centro Stylo Fiat in 1969.

This small barchetta used the same transverse mid-engine layout as the much larger and more exotic Lamborghini Miura of 1966, which had also been designed by Gandini.

The Runabout also exhibited the pronounced wedge shaped profile that would distinguish many of Gandini's designs from this time, including the 1968 Alfa Romeo Carabo.

Around this time there was also growing concern that the United States would shortly implement rollover safety requirements that would effectively ban traditional convertibles.

[8][5] On August 20, 2022, the Runabout participated in the Pebble Beach Concours d'Elegance, entered into the L-2 Postwar Preservation Class, and was named the winner of the Gran Turismo special award by Kazunori Yamauchi.

[10][6] The hood was long and flat with a tapering central indentation and an Autobianchi badge inset just back of the tip.

[12] The only items above the sill line were a low clear curved wind deflector and a foil-shaped forward-swept rollbar similar in appearance to the radar arches on some boats.