I would really rather keep it as 4a for a couple of reasons, even if it was released between Animal 3 and 4. One is that I think/ suspect that the reason there wasn't a Pogo story in Animal 4 is because it was used in Our Gang 6 instead. Another is because, since there wasn't a Pogo story in Animal 4, calling the Our Gang 'Animal 4a' makes sure the Pogo continuity is correct and the story falls between 3 and 5 no matter what. Calling 3a means there's a chance somebody not knowing the history on our files thinks the 3 comes after the 3a for some reason.