Do i have Manual valve body ??

Howdy! I just opened up an A-904-LA case to change the filter before putting it in my Duster. Bought it from a guy who had it in a full size car behind a 318. The plate has 512 stamped in it. Is that stock? I was going to order a shift kit for it but now I’m wondering if it already has one. How do I tell what this thing is? I know the transmission has been rebuilt at some point because of the gaskets poking out between the main case and tail shaft. The guy I bought it from said it came with his car. Any help would be appreciated. Thanks!

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