There was actually four different standard designs. You had the rectangular lights which came as either a 4x6" quad configuration, or the larger 5x7"design with one light on each side. Then there was the 5 3/4" round lights which were also a quad configuration, and the 7" round lights with one on each side. Prior to 1975 there was only the round designs and prior to 1958 when the quad 5 3/4" light configuration were allowed, the only legal headlight was the 7" round design, which itself dated back to 1939.
The reason for the standardization in 1939 was that similar to today, every car had different lights in different configurations, though the main problem then was finding replacement lights when they inevitably burned out or got damaged.
The first car with composite headlights was actually the Ford Thunderbird, but the Taurus is one everyone noticed.
Soggy@lemmy.world 23 hours ago
Switch to one specific LED bulb instead. (Or two! Your choice of circle or rectangle.)