’71 Barracuda Rear End

Looking for some advice: I currently have an 8 3/4 rear end that I just put in a new 3.23 posi center section gear set-up. What is the best gear oil to put in it? I have heard to not use synthetic, to only use synthetic, to use any cheap gear oil with a separate additive . . . just trying to get some opinions!
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Author: Claudia