Back then, the NCAA Team Championship was determined by performance in the NCAA singles and doubles tournaments. So, if you were a team with a few really good singles players, you were golden. I'm not exactly sure how the points were added up. That's how the SEC tournament was for a long long time too, until 1990.
The team format for NCAAs did not emerge until 1979, I think. At that time, only 16 teams played in the team tournament.