The four extant 721Gs were re-bodied and fitted with nose-mounted radiators and the crash-absorbing deformable structures that became mandatory that season; although no new chassis were built, they were re-designated 731s.
Os catro 721G existentes foron voltos a carrozar e equipados con radiadores montados no nariz e estruturas deformables de absorción de choque que se converteron en obrigatorios esa tempada, aínda que non se construíu ningún novo chasis, foron os 731s redeseñados.