Need help Identifying 8.75 3rd member

I would like to put a bit more gear in my 3rd member before I put it back into the car. It is currently 3.23, I would like to go 3.73 or 3.91... I always thought it was a "suregrip" but I am not sure how to tell the difference from a "suregrip" and a auburn type "posi". So which one is this? And what is the difference when it comes time to have it rebuilt?

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