Way back in the day ATP offered a decal sheet with DC-8 windows. I recall most of one side of the sheet, and possibly some of the flip side, was taken up not only with the window differences among the different types and sub-types, but also with differences for aircraft ordered by specific airlines. Douglas was very accommodating to customer requests for specific features (see the larger R1 door on Eastern’s DC-9s, for example). When aircraft built to such bespoke customer specifications were acquired by other carriers through merger or sale, it made fleet integration very interesting, if not maddening.
Jodie Peeler
"In any dispute the intensity of feeling is inversely proportional to the value of the issues at stake." - Sayre's Law