Hartman had three league titles, 72, 73 and 77.
It's arbitrary, but I'd mark the start of the modern era with the introduction of the 3-point line (1986) and expansion of the tournament to 64 teams (1985).
That would eliminate Hartman.
Others might say post-war or the first major expansion of the tournament, which allowed K-State to get the elite 8 as a second place Big 8 team in 1974.