The rarest and most desirable OSCA is the 1600 GTZ built by Zagato. This used the largest version of OSCA’s twin-cam engine with a sleek body design from Zagato of Milan. It was based off the 1600 GT Berlinetta, one of the last made with input from the Maserati brothers.
OSCA’s 1600 used a version of the engine Aurelio Lampredi originally designed for the the Fiat 1500. Denis Jenkinson said the “twin overhead camshaft units, have always been noted for their smoothness and cleanness”. They were housed in a all-indepenedently-sprung tubular chassis, and to make them even more appealing several bare chassis were sent to Zagato for a sporting all-aluminum body.
Two Competizion Allegerita versions were made in conjunction with Zagato. The factory prepared these with stiffened suspension and Zagato fit a slightly lower body. The engine was also upgraded with higher-compression pistons, higher-lift camshafts and Weber 42DCOE Carburetors were fitted. Attached to this was a close ratio five-speed gearbox. Zagato got the weight down to 745 kg by using Elektron alloy road wheels, SZ-style lightweight seats and Plexiglass windows.