Pickup In the Rain

Here in the states, we refer to these trucks as the square bodies.
They are by far my favorite style of Chevy/GMC trucks.
The black body panels are probably aftermarket parts that used to be inexpensive and plentiful here in what we car enthusiasts call the rust belt.
The name comes from living in an area where they salt the roads in winter which in turn effectively dissolves steel.
The bed sides are actually a bolt-on unit with a tiny stitch weld where the panel meets the bed floor on the tailgate end.
The gray primer on the rocker panels indicates that they could have well been replaced and the primer that runs up the cab back looks to be from replacing the cab corners.