Streamlined Thoroughbreds is a lavishly illustrated book published to illustrate the working careers of the Commonwealth Railway‘s GM class, Victoria‘s S class and New South Wales‘ 42 and 421 class of locomotives. These locomotives were introduced in the early 1950‘s to replace ageing steam locomotives and so revolutionised those railway systems. The locomotive design was a modified version of the F7 model for the Electric Motive Division of the General Electric Corporation of America. The contract for the building of these locomotives in Australia was awarded to Clyde Engineering Company Limited of New South Wales.