Thats about what I figured. I was guessing it was worth about $600 because of its mileage. It seems that I was overwhelmed with people wanting to buy it, but no one making a good offer.
I guess I am better off keeping it. Otherwise I am going to spend more money putting a posi into my old 7.5" (80k mile unit). And it will give me the best rear-end that is available for my car, it is almost brand new, its a posi, and it has the same gear ratio my car came with so I don't have to worry about changing the speed sensor gear.
Thanks for the help guys.