Where to buy correct alternator for a 1969 340 swinger non a/c car

Rockauto has 55 and 60 amp alts . some of them say may not come with pulleys or may be square back.
Lack of rebuildable cores is the problem. I don't see any roundbacks at Napa or O Reilly. None listed at Autozone either. Edit: I best look back at O Reilly. Rusty said they have some listed.