Nissan Repair: 1997 Altima Engine Mount, bolt nut, vise grips

Question
Is there a special socket (or tool) that i need to remove the square bolts that
run along the main brace under the car?

Answer
I have never come across a square bolt. What you are probally seeing is the back of a bolt/nut that is supposed to be welded to component. If its spinning when you are trying to take it off the weld is broken and you will have to hold with vise grips.