Specifically, about the ones held in the US in the 1960's and early 1970's. They seem to have featured men's 1600 meter relays, according to the results (including in the T&FN archives).

My question is how did they pull this off? Did they reconfigure the tracks at stadiums like Stanford and the Coliseum as 400 meters around?

Because obviously it's quite difficult to do a 4x400 relay on a 440 yard track. The usual approach in college and HS meets after the switch to metric was to run a mile relay so the passing zones were in the same spot every time around.

What did they do? Did they have 3 different sets of passing zones so they could run 400 meter legs?