Right Josh, here is a photo of the 3prong insert with a 4tab emblem.

And you are saying the 1961 4tab-3prong emblem is different in diameter, and the tab spacing is different from a 1956-60 4tab emblem.
If that is the case then I have a 4tab-3prong emblem, not he 4tab emblem I'm looking for.
Thanks that is what I thought but wanted to check for sure.
Cheers guys.