Well I already feel like an idiot so here's some more pics and another question.

The Pulley

Pulley Width

So the pulley is marginally smaller than the balancer and still likely slightly larger than 6.75". And the pulley is wider, as measured from outside to outside, than 1/2" - really more like 5/8's. But is this what's meant by 1/2" when discussing the pulley width as compared to 3/8?