[8] A tender for 25 replacement railcars was approved by Cabinet in 1944, but World War II delayed the completion of responses until 1947.

[8] In 1949, Cabinet approved a new tender to replace the Wairarapa railcars and other steam-hauled services, which were to have 88 seats and have braking equipment for the centre rail on the Rimutaka Incline.

[8] It was decided that engines for the railcars should be mounted underfloor for increased passenger capacity and for a parcel and baggage compartment, with trussed-chassis to support the braking equipment.

[10] Drewry's tender presented a design for an articulated railcar with seating for 88 passengers, with either Hercules or Fiat 210 hp (160 kW) engines.

[16] The arrival of the first railcars was greeted with enthusiasm by local newspapers,[15] and were described as a "new-dawn for long-distance rail travel" in New Zealand.

[19] Additional Fiat staff and fitters came to New Zealand from Italy and essentially rebuilt the engines and power systems of all the railcars.

[19] In early December 1955, NZR ran a four-day demonstration train from Picton to Invercargill, creating much public interest.

[4] The 1952 Royal Commission recommended railcar services on the North Island Main Trunk and replacing the daylight multiple stops train on the Main South Line (which supplemented the South Island Limited and other fast express services) leaving Dunedin at 8:05 am and Christchurch at 9:40 am on Monday, Wednesday and Friday and replace local trains between Auckland and Hamilton, Wellington and Palmerston North, Christchurch and Ashburton.

[23] NZR requested the calling of tenders for new engines and crankshafts for all 35 railcars plus spares for £1.05 million New Zealand pounds in July 1966.

[21] In January 1967 the Cabinet approved only replacement crankshafts to continue the railcars for five years on the Wairarapa, Wellington-Napier-Gisborne and Auckland-New Plymouth routes[24] and to conduct trials of fast upgraded railcar service between Auckland and Hamilton (later known as the "Blue Streak" service) and Wellington and Palmerston North.

The last trip came to an ignominious end when an engine failure and fire meant that passengers had to be taken onwards from Otira by bus.

[28] Although the remaining services were to areas not well served by road, the mechanical condition of the railcars meant that by the mid-1970s replacement was becoming urgent.

The seating was reduced to 84 to accommodate a servery area from which light meals and assorted alcoholic and non-alcoholic drinks could be purchased.

This was notable as the first time that a regularly scheduled passenger train service in New Zealand had reinstated onboard catering since dining cars had been withdrawn across the network as an economy measure during World War I.

[16] In March 1976, NZR general manager Tom Small instructed his chief mechanical engineer to prepare plans to convert 14 railcars to unpowered carriages.

[31] In April 1976 the chief mechanical engineer reported that 23 railcars were suitable for conversion to locomotive-hauled passenger carriages.

The workshops removed the railcars engines and drivers' cabs, added new lighting, seating, heaters, generators and new vinyl flooring.

[37] Small's successor as general manager, Trevor Hayward, insisted on this scheme, as railway historian David Leitch put to Hayward in a letter that traditional Midland red was associated with poor service,[38] arguing that if the public saw the carriages as just old red railcars hauled by locomotives, that would have negative connotations.

[40] Most of the passenger runs were continued after their demise, but the New Plymouth-Taumarunui service ended on 23 January 1983 (having already had its rolling stock replaced by 56-foot carriages.

Several units along with a Vulcan railcar were sold to the Southern Rail preservation project at Christchurch where they were later scrapped; the cab and baggage car section of the No.1 end of RM 119 on the leading bogie together with some engines and gearboxes were kept at this time.

After the project was wound up, the partial section of RM 119 was moved to Linwood Locomotive Depot where it remained in storage for several years.

Although the car was in a weathered condition and had been cut in half at some point, it was still relatively complete despite missing the seats, bogies (removed in the late 1970s at Otahuhu Workshops), and its diesel engines.

This railcar was purchased to become the replacement for the damaged half of RM 133 and moved to Pahiatua where restoration work began.

The Trust negotiated with the owners of the No 1 end of RM 121 to buy it and were eventually able to do so in 2011 in exchange for two former wooden passenger cars.