This is something i posted in another forum. The one thing i forgot to mention is for the syphon in the overflow you can use piece of u tube.
I am in the process of doing the same thing and have done a lot of research. Here are some ideas for an overflow and sump.
1.)With the overflow the idea is that if the power goes out it will maintain a syphon due to the baffle between the drain into the overflow and the drain out of the overflow.This is extremely important because when the power comes back on your return pump will resume pumping and if you do not have the room in your main tank to handle the some of the water in your sump it will end up on the floor. You can go to home depot or any hardware store and buy acrylic to make the overflow. You can heat it up with a blow torch (make sure it doesn't bubble) and bend it over a straight edge. One more thing is if you plan on running the return line deep into your main put a hole on your return line just below the surface (1/8"-1/4").This is so that if the power goes off and the return starts to back syphon when the surface reaches the hole it will break the syphon.
2.) The sump/fuge design pic should give you a good basic idea of what one looks like. The only thing is that it does not have a bubble trap incorporated. The filter media is optional depending on what set-up you want.
I realize this is a little long winded but i hope it helps you. Good luck.
(If diagrams don't appear Pm me and i can email them to you)
65 gal reef
2 PC's 192W each , 20 gal sump/fuge
4 false clowns, 2 firefish, cardinal, midas blennie, toadstool, zoos, shrooms, trumpet coral, torch, pagoda, frogspawn, poylps, red open brain, devils hand, hermits, snails, 3 cleaner shrimp, coral banded and a emerald crab.