An apparatus for retrofitting a HID lighting system includes using existing components of previously installed HID lighting systems such as its ballasts while replacing some capacitors to adjust the power supplied to a retrofit LED luminaire. Unused ballast drivers are removed, and a self-contained ballast driver assembly is mounted into the electronic control enclosure of the previously installed lighting system. Some of the retrofit LED luminaires include an uplighting lens, an optic, or a diffuser for providing uplight. An aiming bracket and an aiming plate allow for the horizontal aiming angle of a light luminaire to be set.