I'll chime in. I was the friend helping at the time.

The carb jets are free moving and not sticking. The unevenness mentioned is due to each float bowl having a slightly different check valve. It appears the level in one bowl is sitting slightly higher than the other, but only by a cm or so. Not sure if that would cause an issue, but it has for sure been around in that form much longer than this problem.

The abnormally loud valve clicking sounds much more like a knock to me, but because neither of us have heard a real knock first hand, we can only guess. The knock is definitely louder from under the car. The whine sounds like the sing that grows louder as bearings fail, but could just as easily be the alternator I suppose.

The vibration mentioned really feels very much like running on three cylinders, or having 2 of the spark plug wires crossed; both of which I've personally experienced. We have also triple checked the distributor and fire order without finding a culprit. Plus there isn't an associated loss of power.

Very strange issue...