Think I May Have Found Out Why My 340 Seemed to Idle Rough...

Those are converter balance weights. Most aftermarket converters are balanced, much like your tires are balanced. Those are not engine balance weights. Engine balance weights are much larger and are on the forward face of the converter. I bet that if you take that Hughes converter out of the box and look at it you will also see weights welded on it at some point. If not I would be calling hughes to ask if they have balanced the converter.

I strongly doubt this is the cause of your vibration. Does the car have solid engine mounts, is the engine chained down?