OK, measured the axles out of the 88 240 diff I have. Also looked at the 83/84 diffs and they ALL have the bosses case into the diff housing to accept the 7-series central torque reaction rods, so they must have added those when the 760 went into production in the early 80s. Note on the 83s the bosses weren’t drilled and tapped for the 7-series arm bolts, but the 88 was at least drilled and maybe tapped.
Here’s a few rough measurements:
Shaft diameter
at spline ~30 mm, then steps up to 33 mm, then 36 mm, then 40 mm at bearing.
It’s a 27 tooth spline (pretty sure I counted correctly)
The length of the axle from the inboard end to the outer flange mounting face (where the disc would sit) is ~680 mm. The distance from the back of the flange to the outer surface of the axle retaining plate is about 50 mm. A couple pics below. Any other measurements, lemme know.