I recently bought a '71 Dart, 318/904. It has a vibration. The balancer appears OK so I checked the flexplate and converter. No cracks in the flexplate, no missing bolts.

I looked for 360 weights on the converter and found nothing on the flexplate side of it, but on the side toward the transmission; welded to the outside of the converter body; I can feel a weight about 3 inches long and less than 1/8" thick. The converter looks like it might be a replacement, shiny black paint on it.

I'm pretty sure the converter is causing the vibration, but I've never seen weights in that location.

Oh, yeah... and it looks like the vibration has taken it's toll on the starter ring. Not a great pic with the phone in one hand and small light in the other, but it is cracked.

On a good note, I might have figured out the vibration that has kept the previous two owners from driving the car very often.