I decided to buy the retrofit kit with part number 5G1 052 200 C. As explained last week, this is an official kit provided by Volkswagen for the Golf 7.5. The price I paid was more competitive than buying the four tail lights second-hand and sourcing the wiring separately. The only remaining item I need to purchase is the set of replacement connectors, part number 1K8 972 928 B.

Once I receive the new connectors, I will start retrofitting the lights. Until then, there is not much more to tell.

A box full of led tail lights.
A box full of led tail lights.
Led tail lights decently packed.
Led tail lights decently packed.
Left outer tail light.
Left outer tail light.
Back side of the left outer tail light.
Back side of the left outer tail light.
Documentation that came with the kit.
Documentation that came with the kit.

part 1 - part 2