I don't know about the 1950's stuff, but this video shows how a tub drain is typically removed.
http://www.youtube.com/watch?v=N81llf4h_J4
I've used this method myself and it works fine.
Once the drain is out and the walls and floor are gone, the tub should slide out.
I just finished a master bath gut and remodel. Not sure if I ever want to do one again.