The project was aimed to create a road-going sports car that could be sold in meaningful numbers to wealthy customers in an image of Porsche 550 Spyder.

Because Fantuzzi usually realised designs of others, the 150 GT Spyder's lightweight aluminium bodywork was mainly inspired by the work of Pietro Frua, with elements also found on Zagato-bodied Maseratis.

It had smaller carburettors and a lower compression ratio, with a 81 by 72 mm (3.2 by 2.8 in) bore and stroke, yielding a displacement of 1,484.1 cc (1.5 L; 90.6 cu in) and power output of 130 PS (96 kW; 128 hp) at 6800 rpm.

[7] After extensive research by the marque historian Adolfo Orsi, it was determined that the chassis originally belonged to the 1954 Maserati A6GCS and was numbered 2043.

The final iteration of the chassis had to be revised to accept the 150S racing engine, a gearbox casing from A6G/2000 road car, and a 200S prop shaft.

[3] The front independent suspension with coil springs and Houdaille hydraulic shock absorbers remained mostly unmodified from their original A6GCS race car specification.