Here is where I placed the right (passenger side) ballast, which I think is a perfect spot for it...
You are looking into where the stock air box used to be mounted, once it is gone, it has two mounting points, I use one of them, as the ballast is fairly light with a tiny bit of torque it is sitting still with only one bolt. The hard part was fitting the wire through the 1in / 1.5in hole that leads to the headlight, you might want to sort out the wires first and make sure you do not break the pins on the wires from the kit. Other than that... its perfect. The left ballast (drivers side) I mounted on the left wall of the engine compartment where the battery sits.