Ok, that part is the rear yoke or prop shaft yoke, they call it. Here is what they show for part numbers by year:
1940-41.........3665768
No cars between 42-45 WWII
1946............they don't show a separate yoke
1947-48........... they don't show a separate yoke either
However, from 40-48 they show the same part number for the U joint assembly, which is 606779.
1949-50 ......they don't show a separate yoke either, just the transmission yoke, which I take to be the one in front, not the broken one you have.
The U joint part number changes to 591642 from 49-50.
What year rear end do you think you have ?
Don