[McMurphy]

Your Harmonic Balancer is notch/tabbed to fit only one way on your crank shaft, there is no way it could have "slipped". I have seen where they have disintegrated, but that was an isolated event, I think....

More than likely, your distributor is 180* off. You will need to take off the retainer yoke, (the Y shaped clamp holding it to the engine) and rotate it a half turn and re-seat it.
There are many posts (some on this site) on how to do this.

I am 99% sure that is your timing mark problem.
Good luck !