Actually the breakdown should be 73-80 and 81-87.
Front fenders are different.
Hood is different
Hood cowl (where the wipers are) is different
Radiator core is different
There are differences in the shape of the dash pad and the bezel.
Various differences in gauges over the years.
Earlier year door panels are different.
Starting in 79 they started to use the gas door.
After 78 model years, they started to use cats.
Tailgate differences requiring year specific tailgate panel to be used.
Mounting locations for truck bed are different, I believe.
These are some that I know of......
