Since its the driverside (sorty) you can get one out of any F150, F250 or fullsize Bronco truck in the junk yard cheap. It will need to be cut 1/2" off the end of the splines where it goes into the carrier. Don't worry about the cut, it still has full engagement on the carrier.
I use a cut off wheel. The stub shaft (outer) is the same length. I have neen running F250 D44 shafts for years in my 68 D44 using the 760's on 38's and seems to hold up, now I break hubs! On the full size shafts, the passengerside (long shaft) has to be cut down 6" and resplined in a machine shop.