replacing the torque tube with an open drive adapted to the original diff has been done ,, BUT ,, it is a significant engineering exercise and not worth the effort .
The replacement of the original with a '55 pickup unit is less work than the above , and is a good option to consider , ( I am biased , I have done this to my '40 , and am in the process of doing it to a '37).
Fixing the leaks you have is not all that hard ,, you say it needs repairs ,, what is the trouble there ? ,, maybe it is just a small fix too .
