I found this for sale. Let me ask the big question first. Would this work for a typical 75g tank?

I got a few of these from a warehouse. It's a 400 watt metal halide setup and could be used as is just by putting a reef bulb in it (I will send the bulb it has with it but its just a standard 400w bulb that you would find in a warehouse). The plug is also an industrial plug you would want to switch to a standard plug. I think those go for about $4.00 at home depot and are simple and easy to put on.
The ballast is mounted above the light and reflector with a hook on the top of the ballast to easily mount it. The total length is 21" from the top of the ballast to the tip of the reflector. If you are electrical savvy you may know of a way to make the ballast remote.