There are 2 different "Ambulance Alterbators" pictured in that auction for one alternator. I have posted the pictures from the auction of the back of both of them. Notice that one has screws at the top, and the other doesn't. If you study the 2 pictures, you will also see other differences. There is no description of the item that you are buying, so I have no way to know if it is for one or two units, since the pictures are misleading. I have asked the seller this question, and am awaiting his answer.
Considering that if you were to need parts to repair that alternator, which is a very common occurrence, that you will have to do a lot of searching for those parts, since it is obsolete. Even the diodes for a 1960's or 1970s GM/Delco alternator are extremely difficult to find. I would advise anyone that is interested in purchasing this, that they should consider it a "core" that will need rebuilding, unless the seller were to guarantee it as a working unit.
there used to be an independant rebuilder in Pearl River NY that did a fabulous job rebuilding these but he is no longer in business. There is an independant rebuilder in Kent WA (The Rebuilder) that does these.