Please help me ID this trans & case

[Joe J-Truck]

I think its a D20 behind an early warner Auto tranny. Somebody told me it might be a D21. I'd like to know how to tell a D21 from a D20. It is evident this was not the original tranny. A p.o. swapped it in place of a manual.
It is in a 62-64? (not sure of year) j200 with the 230 ohc engine.

[joe]

If the original trans was a manual it's a D20. The D21 "only" hung off the BW AT in the Wags.