sentences:  Early tests in 1974 proved unsuccessful until a special non-creep rubber was developed by the Malaysian Rubber Producers Association.This was formed into springs by the Aeon Products company and following more productive testing results, fitted to the car from the 1975 Argentine GP.Originally, Lord Hesketh had plans to fund and have built a V12 engine to accompany the car, but this never came to pass, and the DFV V8 was used exclusively.