Originally built in 1964 as 744M, to the same design as 795M.
Extensively stripped and modified by Commonwealth Engineering of Dandenong in 1982 to have the same controller, desk layout, airconditioning and interior as the \"Comeng Supertrains\" then under construction. 8 motor cars and 8 trailer cars were modified in this way
The number then alternated between 903 and 603M several times during 1983-1984 as the Comeng order was extended.
Ultimately the upgrades were considered a failure and not continued. Cab visibility, a major issue of the Harris trains, was made worse by the seat being moved further back. While the cab and interior had been upgraded, the underfloor electrical equipment and motors that drive the wheels were not, and the extra weight of the airconditioning and soundproofing caused acceleration and braking to be considerably slower. As a result, these sets were limited to the relatively flat and short St Kilda, Port Melbourne and Sandringham lines.
The cars were all retired by 1991. Some were modified again and remain in service with V/line, used on short distance commuter trains.