An LED lighting kit comprises an extrusion (300), an LED strip (100), a tapered wedge (1500), and a mounting clip (1200). The extrusion itself may have a recessed linear groove of sufficient width and depth to seat the LED strip. The clip is sized and shaped to springably engage ledges (320) in a first channel (310) of the extrusion when the strip is mounted. In one aspect, two extrusions are butted end-to-end and are aligned by inserting the tapered wedge into the first channel of each extrusion prior to butting them together. The extrusion contains a second channel (315) that houses the LED strip. A translucent diffuser (900) is springably inserted into the second channel, thereby diffusing light that is emitted by the LED strip.