Save the heat, you do not have enough room to use HID lights unless you buy a cool tube and a vortex blower to keep the heat away.

If it were me I would use 48? florescent lights but relocate the ballast outside the grow box, again to save the heat. You could use one of the 125w compact fluorescent lights too. Line the box with Mylar to maximize the light reflection. You will need fresh air in and internal air movement inside the box. What about odor control?