Kinda blurry, since it was a cell phone shot, but you can see it on the bottom left here:
http://d3j5vwomefv46c.cloudfront.net...6qjlqM21~dRiA_
The new mount is next to it for comparison.

Is this an Emperor's New Clothes thing? (I see no pictures!)

D'oh, it works for me. Let me try that again. Should be able to click the thumbnail below to get a larger version
http://twitpic.com/show/thumb/91gi5q.jpg

Wow that's seriously out of whack - they must have lifted the car on the mount with three fat ladies in the back...

I'm guessing that'll sort out the tyre wear problems.

Different axle types
 

Will those axles interchange?

Yes, the axle looks different but the overall length is the same and it went in fine. This is the "First Equipment Quality" Chinese replacement one, so we'll see how it holds up. It's obviously a non-homokinetic axle adapted to the homokinetic application, but I'm OK with that as it'd make future axle changes much easier...

Yeah, it's a puzzler. The only other thing I can think of is a hit on the rear subframe, but if that happened I'd have a lot of other bent parts.

The car has had a long, adventurous life, including a stint with a wooden boat builder who used it like a pickup truck...so who knows.

Welp, having test-driven it I can say that three things are already obvious:
- The back end jumps up less when I shift into reverse.
- There's less driveline vibration (probably due to the new axle)
- There's less of a "rear steer" sensation when I corner hard.

Oh no - you've lost that rear steer ability. That's not good how are you going to parallel park now?

The Bottom Axle looks like an Annular Axle.
If he bought new a new Annular Axle made in the Far East he should remove one Bolt at a time and re-install them with Loctite.
As they have a reputation for having the Bolts come loose while driving.
A recent thread on that over on Benz World.

The top pic is Homokinetic Axle.
You can use either type of Axle as long as it is made for your year and model.

Yikes, good to know. I'll keep an eye on it. The bolts were match-marked with paint so if the paint marks start to drift apart I'll know to Locktite them. Will take a look next time I have the car in the garage.

Heehee. Not much good for parking when it only kicks in during 60 mph lane change maneuvers. ;) Something tells me I'm not gonna miss that queasy "tail wagging the dog" feeling.

So, after reading some horror stories about the bolts working loose on these annular-type replacement axles, I decided to take the bolts out one at a time and put thread locker on them. The bolts on mine were still plenty tight (I've probably only put a few hundred miles on it) but, sure enough, there was no thread locker on them. In fact, they seemed to have anti-seize on them, instead. It was an annoying job but not difficult...took maybe an hour, and I'm slow. Plus I was working on the left side where the exhaust is in the way.

I can't believe it. Do you think that the under age poorly paid children who assembled your axles were dipping the bolt threads in the wrong bucket of goo?

Could also have been CV grease from sloppy assembly, I suppose. There was definitely something oily/greasy in the threads, and the odor reminded me of antiseize. I cleaned them with brake cleaner before applying the thread locker.