How would you plumb this?

[jvision]

I'm wanting to set up my 90 gal in the next couple days. It has 2 x 1.5" drains in the bottom and 2 x .75" returns up top.



My 1st idea was to turn the 2 drains into a Herbie system, and return thru the top... but I was thinking that I'd only need 1 of the returns.
Now I'm thinking of doing a Herbie out of one of the top holes, and returning thru the other, and making the 1.5" holes a closed loop.
I've got extra glass to make an overflow box, and I have gobs of 1.5 and 3/4" piping, but what fittings will I need to make this all work? How do I set up the closed loop on the inside (think I can figure out how to do everything under the tank)?

Thanks, all!