Thanks for the response. One question please. Is the 56.3 inches measured a set distance from the low beams?rburns,
A search of the 2015 factory service manual shows that there is no horizontal headlight adjustment possible, only vertical adjustment (dependent on different wheel sizes and H6 or H4 engines I surmise) and I suspect your 2013 is the same.
If the unibody is entirely correct in all dimensions from the factory (meaning that no body repairs have been made which are out of factory specifications) then the headlights can only be installed to be in proper horizontal position when finally fastened in place.
If your headlight is out of alignment, the only thing you might do is to put a washer or two behind the headlight attachment points on one side before you insert and tighten down the bolt. Be aware, though, that your gaps around the headlight and body panels will change and may make this impossible.
The factory distance between the exact center of the two headlight low beams is 56.3 inches, so if the passenger side is correctly positioned, you can go from there. Again, this is on the 2015 model. Good Luck!