more out of 5.9l 360 magnum

You have all the parts. If you pull the heads, you may as well dis assemble the rest. See where the deck clearance is. If the block can be decked to zero, do it. As Bomby boy suggest, attention to the heads is a good idea. I would fully port them though. IMO, if you're gonna do it, DO IT.

Nitrous is ok. It does work. You need to understand though, the engine needs to be built for nitrous for best results. Just throwing nitrous on an already built engine often times does not give optimum performance. Just food for thought.