Consequently , Stampe et Vertongen was asked to adapt the design to the alternative powerplant .
However , the new Minerva engines cost 50,000 BEF while the government could purchase war - surplus Hispano - Suiza engines from France for only 6,500 BEF .
Stampe et Vertongen was asked to adapt the design to the alternative powerplant .
However , the new Minerva engines cost 50,000 BEF while the government could purchase war - surplus Hispano - Suiza engines from France for only 6,500 BEF .