Why not take the alternator apart. Remove the bearings. Take them to a bearing supply place or altenator shop and get replacements. All that has happened is a bearing has failed in there. Very common. If unable to remove the bearings an alternator shop can do it for very little once you have the alternator apart.

You fellows are aware the slip ring can be replaced on these alternators as well. They see so many miles they sometimes have very deep grooves worn in them.

Actually this is a very cheap part. The problem comes after you install the new one. It has to be trued up on a lathe. I have been toying with the ideal of doing a general reconditioning on all my older alternators that are showing wear. Some may still be the original units for all I know. As is stated a lot comprehensive records with an old car are important.