At the time, Carroll Shelby was seeking to find a suitable replacement for his 289 Ford powered 'King Cobras’ as the ’65 USRRC racing series was fast approaching and he was driven to find a superior solution to outperform the 7 liter Chevrolets being developed by Bruce McLaren’s team. He turned to racing friend, Alejandro de Tomaso, as he knew that de Tomaso was an innovator as he had proved with his racing and first road car, the Vallelunga, which featured De Tomaso’s signature advanced lightweight ‘spine’ chassis. The intent was to put their joint project into production and provide it for sale to private racing teams.

The basic understanding was that Shelby would provide the financing, Alejandro would engineer the car and Peter Brock would provide the design and the fabrication would be conducted by Fantuzzi. The collaboration began on the hopes that De Tomaso would provide the chassis and convert Shelby’s 289 Ford/Cobra engine to 7 liters. The conversion of the engine to 7 liters was a key part of their partnership in order to compete with the big block Chevrolet engines.

The Shelby-De Tomaso “Prototipi” was known as the 'P70,' or ‘70P,' due to its planned 7 liter engine. However, over the course of the project the combination of two strong personalities and ulterior motives led to the dissolving of the relationship just before the cars completion. Shelby withdrew from the project as he was being enticed to turn his focus to the Ford GT40 race program and was displeased with the fact that he still had not seen his promised 7 liter engine.

This parting of ways left a “chip” on Alejandro’s shoulder who would then see the project through to completion with the assistance of coach-builder Ghia. The vehicle was displayed at the Turin Motor Show in 1965, renamed the 'Ghia-De Tomaso Sport 5000’.

Before commencing the racing program, Alejandro revised the design and produced a second car under the Sport 5000 name. The combination of its 726 kg dry weight and its powerful powertrain enabled it to be compete with the best of the period. In 1966, the car was raced by Roberto Bussinello in Round 8 of the World Sports-car Championship, but retired on the opening lap. The Sport 5000 was never raced again.

"The Shelby - De Tomaso P70 remains as the sole mechanical tribute to what could have been a successful partnership. With its innovative super light central spine chassis and integrally mounted, load-bearing Ford V8 engine the P70 had a power-to-weight ratio that would easily match or beat the best in the world." - Peter Brock

Alejandro, upset with Shelby leaving the P70 program, used his extreme impetus and took the chassis developed for the P70, strengthened the frame even further, and used it as the basis for his next production model – the De Tomaso Mangusta.