Just my opinion since I don't know the actual composition of the aluminum, but I have experimented a lot with cleaning alternators and Carter AFBs. Those alternators like the carter AFB/AVS have a zinc portion that seems to reside near the surface. Your never going to get the original finish. Period. In my opinion. You can't rezinc them nor get the original mold finish if you have to clean them. The elements and aluminum corrosion have taken there toll. They do not like the acid compounds used to treat other types of carb bodies.

The proper glass at the proper pressure is what is used on carbs and I have used it on alternators also. So you need to experiment. Tumbling with some of these synthetic materials also can change the surface and polish the aluminum, timing is again critical for the final finish you want.

I clean them with an alumaprep treatment followed by the Alodine 1001 (clear/white). Time sensitive and tends to darken the aluminum some the longer it is treated. But it is a conversion coating to help protect the aluminum.

A lot is dependent on starting with an alternator that has never been rebuilt to start.