When the extended trailer cars entered service they were coupled to the new M cars, which had their power-closing door equipment activated or installed as required. The first set was 799M-891T-892T-800M (order unclear), and two more blocks were assembled using four of the seven motors in the range 792M-798M. In 1972 further cars 791M, 887T-890T and 557BT-560BT had the same equipment installed, giving a total of ten motors, six extended and four regular trailers and four backing trailers available to assemble three Long Blocks and four Units fitted with power door equipment. At this point, the total fleet would have been 62 Short Blocks, 3 Long Blocks with power-closing doors, 4 Pairs, 52 normal units and 4 Units with power-closing doors.