it will help with the longevity of the motor, plus it will be more efficient. If you're going to spend the money getting it nitrided, knife edged, etc. you may as well get the motor 0 balanced. Typically 302 motors are balanced with a 50z, doubt that you would want that excess weight slinging around on the nose of the crank...
Not required, but would be a good idea, especially if you're going to spin it north of 7500...
also, NASCAR motors spin for one race then are rebuilt...

Just my opinion though..