300TD Engine Balance

I hope some one can answer this. The Harmonic Balancer on my 79 300TD came loose. I've ordered the lost retaining hardware, but since it free wheeled on the crank shaft, I don't know where it was originally positioned (radially). The MB parts dept in Knoxville tells me it doesn't matter, which makes no sense.

Is the balancer self positioning? How can that be? Help.

I just bought this car and I love it! 1st Benz. Quirky, but lots of charm, classy, but best of all, my wife hates it.