Chevrolet Low Cab Forward 4500 2019 Series Owner's Manual page 297

296 Technical Data
The engine number is located on
the left side rear part of the engine
block and the right side front part of
the oil pan.
Option Codes
The ID plate at the lower part of the
righthand door striker indicates
option codes. These codes are
three-digit, alphanumeric codes,
each assigned to a particular
component of the vehicle.
You will be able to use these codes
to identify the model or type of
engine, transmission, rear axle or
other components when your
vehicle needs inspection and other
services.