Yes, you can gravity feed a skimmer from an overflow. Then have the skimmer's outlet pipe drain into the sump/fuge.... saves the expense of a pump.
There's a thread around here somewhere with a parts list....found it.
http://reefcentral.com/forums/showthread.php?s=&threadid=699977&highlight=skimmers
Here's the overall construction.
Here is the best shot I could come up with, kind of difficult to get a pic back behind the tank.
The bulkhead (black object partially blocking the view of the farthest pump in the pic) feeds from the overflow box to the inlet of the pump. The overflow bulkhead is 1 1/2" but is reduced down to 3/4" just before it connects to the pump.
The outlet of the pump is 3/4" also. Pumps straight up to the tee where it is reduced to 1/2" and feeds out to both skimmers.
If you follow the second skimmer in the pic downwards, you can just make out the lower tee. It comes up in 1" pipe, through the gate valve and into the tank.
In your applicatoin, just feed the overflow to the upper tee of the skimmer (which will have to be a little lower than the overflow, so you will have to adjust the heigth of the skimmer body accordingly). Plumb the lower tee to return through a gate valve (ball valves are too difficult to get a fine adjustment) into the sump. It will probably be beneficial to run the outlet pipe straight up as high as you want the water level to be before turning it back downwards to go to the sump. Then where the outlet pipe turns (up at the top), place a tee instead of a 90 to create a vent. Otherwise you will just be creating a siphon and the water will go like a tiolet...flush...flush...flush...over and over which will bounce your water level inside the skimmer up and down as it flushes.
Having the water pumped, I am using a 480 gph to feed two skimmers. Tschopp told me that the flow rate will be limited by the body of the skimmer. I think he said somewhere around 300 gph for a 3" body. I don't know what your overflow rate will be, but you may have to use a bigger pipe for the inlet and outlet tees (if you go with a three inch body). If your overflow rate is more than that, you might consider even going up to a 4" body. I don't know about only feeding one overflow to the skimmer either. Ideally (theoretically), the overflow rate through one box would be 1/2 of the total and would be constant. In dynamic action though...???...if the rate through one box varies by much at all, it will affect the water level inside the skimmer and affect it's performance. Just have to experiment around with it and see how it works. Maybe put a pump on it if the water level is going up and down inside the skimmer too much.
I didn't glue the riser pipe either, You may find it prudent to glue it, and then maybe install a union to be able to remove the riser pipe for cleaning. It doesn't matter to me if the pipe leaks a little water every now and then, but probably not a god idea in your basement.
Hope that's not too confusing.
. You are going to have to figure out how to automate your water changes too man. Your going to have ALOT of water in there 
speaking of that, i still need to go buy a laundry-style sink basin and plumb it to the washer/dryer drain and water supplies. i need to get on that, actually.
