Need help identifying early A-body auto trans

Thanks so much for the help; there's just no substitute for experience and this forum shares it in abundance!

I pulled the trigger and bought the car; it's a '66 Dart GT with a '74 built motor (.30 over, shaved head, port work, Comp cam (not sure which grind) Super Six manifold with Weber carb and Dutra duals front manifold, the aforementioned 904, power steering (please don't laugh; living in San Francisco and parallel parking with 5 1/2 turns lock-to-lock manual steering is no picnic with 215 tires and 2 degrees castor!), large bolt pattern all around with single piston disc brakes in front and, best of all, an A-body 8 1/4 Sure-grip with 3.21 gears.

The interior is sort of rough with some kind of generic aftermarket bucket seats, but the headliner is clean and the cool console is in pretty good shape. No major body crunches or rot; have to hit it with clay bar and see what the paint looks like under the oxidation.

Game plan is to swap the engine, axle and power steering into my '63 Dart GT with the tired stock 225, 7 1/4 2.76 axle, manual steering and close-ratio A833...should be fun!

Hopefully the 904 will prove to be what we think it is and the '63 225 will bolt up with the appropriate flex plate.

Thanks again for the knowledge and willingness to share it