This day was before my time but I have studied this event some. I remember how everyone was talking up June 5, 2008 as being similar, however ended up being a bust.
Anyway June 8, 1974 was a very unique and potent setup for tornadoes, especially for so late in the season. You can find a few weather charts for this day here:
http://bangladeshtornadoes.org/UScases70to84.html.
Just think about these conditions if you were a storm chaser near OKC on a muggy June afternoon.
SPC has likely gone with a high risk and a PDS tornado watch has been issued for much of OK and KS. Its 2pm and its 85/74 at OKC with a southeast wind of 20kts. A pronounced dryline buldge has developed to your southwest, south of a 992mb surface low which was located in southwest Kansas. Lawton was 99/53 with a southwest wind of 20kts! An outflow boundary was draped from northwest to southeast across the northeast third of Oklahoma. A potent upper level low was spinning over western Kansas with diffluent H5 winds of 50-70kts. On top of that LI's are -9 to -10! How excited would you be as a chaser?