Vibration in engine- help!

Based on your original post, the car had been running well up to that point. So I doubt if the flywheel is out of balance. They just don't "go ut of balance". Either they are or they aren't and you would have had a vibration long before now. Harmonic balancer is another story. The rubber deteriorates between the outer ring and the hu, allowing the outer ring to slide and or wobble. You can try to check it be turning the fan belt and see if the outer part of the balancer turns while the inner part stays put. Easiest way to check is with a timing light. Pull and plug the vacuum line to the distributor. Connect the TL nd fire it up. Is th timing maek where it should be (whee it was last time you set the timing)? Is it jumping aroundd as the engine idles? You do have a timing light, right?

Try Rockauto they may have one, or Carquest if you have them in your area.