1983 300SD brake light-cruise control interface

The plate that holds the tail light bulb sockets has one empty hole which lines up with a red lens cover on the tail light lens. I want to add a brake light socket and bulb in that opening to increase brake visability, which is not the brightest on the older MB. But, I read somewhere that if you do not use the proper brakelight bulbs, it will mess up the cruise control, and if I add two bulbs, will it mess it up.

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