51 14 008 Replacing letter/number combination on front left or right side panel
WARNING: This page does not describe the selected car, but rather 21 other vehicles, including the 2017 BMW 550i GT xDrive, 2017 BMW 535i GT xDrive, 2017 BMW 535i GT, 2016 BMW 550i GT xDrive, and 2016 BMW 535i GT xDrive. However, it is still accessible from the selected car via links, so may be relevant.
General procedure is described in:
"REPLACING REAR MODEL DESIGNATION "
Use same procedure as for the front side panel.