Hi Andy,
Something looks fishy in your photo. All the BBB cross-sections show that the shaft journal is shorter than the inner race of the bearing, although all the bearings shown in the BBB are left axle shaft bearings. The BBB does not show a cutaway of the right axle shaft bearing. Your bearing is obviously the correct bearing because I can see that the spherical rollers are cocked in your photo, making them visible from an edge view. If you look at the closeup photo that I posted in reply 841 on page 34, you can see that the shaft bearing journal does not protrude beyond the inner race as yours does. That bearing puller that I show had not yet moved the bearing on the shaft. The flatted "inner race clamping washer/nut locking plate" in intended to clamp the inner race only to keep it from spinning when the nut is tightened. The bearing must be seated firmly against the end of the journal. Your confusion is logical. It looks to me as if your axle shaft is not correct. It certainly does not look like those in the BBB or the one in my 67 230SL. If your bearing was not seated because the clamping washer and nut could not be tightened against the bearing inner race, that would explain also why there are wear marks on the journal. I would think that the inner race has been rotating relative to the shaft. A definite no-no. On the other hand, that would permit the axle shaft to plunge in and out by the length of that gap that you identified. The axle position would be maintained only by the "press fit" of the inner race on the shaft. Scary. Maybe the axle shaft has been changed in the past? Maybe it's time for an expert Mercedes mechanic to provide an opinion to end my speculation and your worries. Joe Alexander? Dan Caron? Anybody else who would know?
Tom Kizer