Its always a good idea to have it balanced after a rebuild. But if its completely taken apart it will need to be balanced, period. Otherwise its 99% likely that it'll trash itself really fast if its off balance. Look at the 'nut' on the end of the turbine shaft. You'll notice how its been ground away at wierd places, that was done in accordance to a computer balancing machine to ensure a nice balance, so it doesn't spin off axis and contact the housing at 50,000 rpm or however fast they spin when fully spooled up.