ETS purchased an additional 31 T6H-5307N diesel transit coaches from General Motors for 1974 delivery. The coaches were about $50,000 each, for a total cost of $1,550,000. The buses were mistakenly delivered as #591-621, and prior to entering #601-621 were renumbered as #301-321.
These 31 buses were the last buses purchased by Edmonton to have standee windows until BBC #100 arrived in 1981. This was also the last order to have folding rear doors, although, ETS would continue ordering dual stream doors on all of the 40' bus orders. Units 591, 592, 593, 310, 312 and 314 were sold to Fort McMurray in the mid 80's. 596 was scrapped after an accident, 309 was sold to Busex in 2000, and scrapped in 2001. 319 was out of service, but returned for the 2001 Track and Field games, and then was sold later in 2001. 317 was retired and sold at auction. 316 was auctioned off in 2001. 305 and 308 were leased to Red Deer Transit commencing in the Fall of 2004. The last units in service were #s 597, 301, 302, 303, 311, 315, and 320, all of which were retired in mid-to-late 2007. #s 317-321 had hard shell seats, the only ones on an ETS GM bus (Popularly referred to as "The McDonald's seats" due to the beige fibreglass frames and red + green vinyl inserts)! #s 597 and 320 were the only units rebuilt into the blue and silver ETS scheme. #320, being one of the first blue and silver rebuilds, received a few variances such as small fleet numbers, all-silver doors, and anti-glare black paint around the driver's area on the interior. Those were features common to the very first buses painted into the blue and silver.