The front bearing was originally open and was the same bearing as was used in the later Delco alternators all the way through the 80s. Even back then though replacements were sealed bearings and thats what you would get now. It is a standard 6-203 bearing. The rear bushing originally had an oil groove cut in it and oil wick. Most rebuilders or suppliers will sale you the solid bushing with no oil groove. These are "self oiling" or "oilite" bushings designed to let oil come out of the bushing and oil the shaft when friction heats it up. I supply both bushings but always cut the oil groove in and install new wicks regardless of which bushing it is. Not all oil grooves were cut in the same spot so I cut the groove where I need it. So the rear oiler becomes functional and the front oiler is just for looks with a sealed bearing.
Ken