Thats the crank cam relation and most Important. If the engine doesn't start, lift the distributer just enough to turn it 180 degrees ( half a round ). The way the distributer keys into its driver will only let it go in one way or the other.
One thing that hasn't been mentioned is PRELUBE THAT NEW CHAIN !
Sink it in 90w gear oil before you install it. To run it dry would shorten its life.