Well, I managed to find 2 low mileage axles for my 81 380sl, and I began removing the passenger side axle using the technique dmorrison wrote up for the 123: http://www.peachparts.com/shopforum/diesel-discussion/220000-w123-how-replacing-rear-axles.html

However, there apparently wasn't enough room between the diff and the hub to get the axle fully out, even after I removed the bushing that secures the diff to the floor, and I raised the diff as far as it would go.

I was therefore thinking that I needed to remove the back seat and side panels, so I could loosen the top shock nut, and drop the axle carrier slightly. But the manual says this:

"Do not loosen shock absorbers since they are required to hold axle."

"If the rear axle shaft cannot be removed in spite of being fully telescoped, loosen rubber bearing from frame floor and rear center piece from rear axle
carrier. Lower center piece and swivel to one side. Then remove rear axle shaft from rear axle shaft flange."

I'm assuming that "rear center piece" is MB-speak for "differential," and the rubber bearing is the one that secures the diff to the floor, which I already removed. But I don't understand what " loosen . . . rear center piece from rear axle carrier means."

So I was hoping that someone with a lot more knowledge than I have could tell me, hopefully tonight, the best way to get this axle out of the hub.

Thanks very much in advance for the help.