Mystery trans, pls help ID

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The options are find someone who is doing a full restoration on 66 Coronet with a 318 poly with a factory 3 on the tree or get scrap price for it.

Ever hear the old saw of “wish in one hand and poop in the other”? That’s where you‘re at with this gear box.

The chances of finding a leprechaun riding a rainbow striped unicorn are far more likely that finding a buyer for that boat anchor.
I haven't researched it enough to know if it was used in what yrs. I'm thinking that it was standard ( no pun intended) equipment on mopars from the late 50's thru 67, which greatly increase my chances of selling it