A simple task for once, but in reality this is only a stepping stone to the De Dion ears install.
The driveshafts are different lengths, so make sure you install the LH on the left-hand-side and RH on the right-hand-side. I smear a tiny bit of oil with my finger on the seal mating surface to protect the driveshaft seal from damage during install. I don’t use any spline grease on these splines, because they are inside the differential and will be bathed in oil.
Now just remove the bung from the differential and insert the driveshaft, it should be as simple as that.