The 1973 oil embargo pushed Detroit into panic mode trying to conserve fuel without sacrificing size, and then the 1975 Energy Policy Conservation Act established the first CAFE standards driving overall fleet fuel efficiency. There wasn't much in the mid-70's that was worth much in the performance arena. That's why so many shows say 1972 and older for participation. The muscle car era ended in 1973, and everything after that was nothing like the older stuff for too many years.