My 1982 MCC has vertically stacked headlights!!
....so went searching and according to:
http://67-72chevytrucks.com/vb...wthread.php?t=298153

quote: Single rectangular headlamps in GM trucks in 1980.
In`81 GM started using quad lights,
one on top of the other,
in the "optional" front end appearance.

...which probably means that the MCC builders/designers were using right up to the minute styling!!