This site helped me figure out ford casting numbers.
http://www.fordification.com/FAQ-datecodes.htm
The short answer is there will be a 3 or 4 place code cast in the houseing that looks like it has screws on each end. For a 56 the first two should read B6_ . The B stands for the fifties and the 6 stands for the sixth year. The last numbers are the month. The forties would begin with A and the sixties with C, seventies D.
As for hooking it up to a flathead it should be possible with the right bell housing. Though the right bell housing may be a modified ford one or a aftermarket. Ford had a tendency to use off the shelf parts in cars so it may even bolt right in. (though not likely)
PS i had that tranny in a 58 fairlane, real nice! it would go faster than I would let it. Pull the lever on the dash to engage it. Push the pedal down and when it topped out let off and let it coast, then as you pushed the pedal down again it re-engages with the motor at an idle. before the pedal is all the way down again the speedo was climbing past 120. I never did top out that 130MPH speedometer.
There was also a switch under the throttle pedal for something.

