and wood can get along as long as you observe a few things.
the envelope of the bulb is 500 degrees, but that heat is pretty much trapped there - the air around the bulb keeps it well insulated - what you end up with is about 150 degrees of radiant heat, most of which bounces off your reflector and into your tank.
the rest needs to vented out of the light fixture somehow.
I built my MH
light out of a wood box, lined with an aluminum reflector. to keep things cool, I used spacers between the aluminum and the wood, giving it about 1" of air gap. I also drilled a hole in the 'top' of the wood box for hot air to chimney out of.
when the light has been on for some time, the sides of the box are warm, but no where near being dangerous - cooler than several aluminum light fixtures that just use fluorescent bulbs.
check out www.hellolights.com
... they have a lot of parts and pieces - you might be able to come up with something and we're here to help