Received the new alternator for the tune of $184. Installed and the tractor humms like a champ. No vibration or noise that was experienced with the previous that would end up shear of the mounting bolt. In comparing the old versus the new I believe that I identified the problem. The pully is made up of two halfs that are pinned together by a spring pin (no sure of the proper terminology) The pin either broke or worked its way out, which allow the outmost half of the pulley to rotate freely instead of spinning true with the alternator shaft. I believe this caused all of the excessive vibration due to an out of balance situation. I am going to see about getting it re-pinned and will use as a spare if I have any future issues with the alternator. What a difference it makes to have the luxury of comparing a problematic part to one that is new.