Volume 3 of the history of Commonwealth Engineering picks up the story where volume 2 left off. The company continued to grow steadily in its rolling stock business, and expanded into new fields. Highlights included the design and construction of the Indian Pacific trains, coinciding with the first standard gauge passenger train services from Sydney to Perth. The design and construction of the interurban double-deck trains for the NSW Railways for service to Lithgow and Gosford were the first such double-deck, air conditioned electric multiple units in the world. In Western Australia the company designed and built the 150 kph Prospector railcars -- Australia's fastest train in those days. The takeover of rival firm A E Goodwin allowed Comeng to enter the lucrative and very successful business of building Alco-powered diesel-electric locomotives, for the growing iron ore mines in Australia's northwest. A new plant at Mittagong specialised in the construction of freight rolling stock. The South African plant -- Union Carriage & Wagon -- grew at an unprecedented rate, turning out multiple types of passenger trains, freight wagons, electric and diesel-electric locomotives, as well as the world-famous luxury express, the Blue Train. The Queensland plant produced large numbers of aluminum wagons to service the expanding coal mines in the state, also producing diesel-electric mainline locomotives and a steady stream of narrow gauge industrial and cane locomotives. In Victoria the company began the production of a new generation of tramcars for the Melbourne system. In South Australia a very successful company was established to design and supply specialised track maintenance machines for use by all the Australian railway systems. The company's long-established business of building buses and other road transport vehicles continued, as did the arm of Comeng that supplied curtain walling for the high rise buildings around Australia. A large industrial arm of the company became a substantial supplier of earth moving and mining machines, industrial ovens and fans, and other similar equipment. The company was now the largest rolling stock manufacturer in the Southern Hemisphere.