There's an economical reason for the change in lighting. They sell those cruisers at end of service, if they aren't totaled first. Frankly, I have no idea why anyone would buy an engine which had been run like that, but some do. Those single lights had to be bolted to the top, with the necessary damage. The light bars clip into the rain gutters on the old Crown Vics and they have methods for clamping them onto other cars. Once you have the light bar in place, well, why not mount more lights? Maybe easier to see...Going through more old slides.......here's a couple local sisters I knew leaning against my Chevy Vega wagon. And one of local police units on patrol. These were taken in the '72-'73 time period.
These times for me were very pure, as compared to today. (back when patrol cars only needed one light on the roof! )