74 dart vibration problem.

Its possable someone put the wrong balancer on the engine, it might have a balancer from a 360 (which is externally balanced) on a 318 (internally balanced). If your balancer has half moon shaped piece of iron on the front it's for a 360 and will definatly cause a vibration if used on a 318.
Yup, a 318 should have a symetrical balancer with no weights or cutouts. The same way with the torque converter......no weights. Hey, I just noticed that you're here in San Diego. Drive it by and I'll take a look/listen and give you my opinion. I'm in Spring Valley, how far away are you?