A Couple of other things...

To complete your questions, these headlights were used near the end of operations because they were available, primarily from scrapped "Broad" Gauge engines. That they gave the engines kind of a family look was incidental.
The smaller headlight and back up light on #70 were 15" diameter Sunbeams, like the ones used on D&RGW narrow gauge engines. These were scavenged from scrap, too.
#72 also had one of these smaller headlights after the Como Roundhouse fire. It had carried an older box-style headlight before then. That headlight, typical of C&S Narrow gauge, also had an 18" diameter lens. So do the CB&Q "Cukoo Clock" style, like those used on #60, 71, and CB&Q #537.
Hope this helps.