I think I found something, please look at the pictures bellow. These are the "end-pins" that go into the star-adjuster of both the new (left) and old (right) shoes. It is quite clear the pin on the new shoe is much longer, and this might be the reason why the drum will not fit over them once they have been installed.

The pin on the old shoe roughly measures about 9 mm, and the one on the new shoe measures 12.5 mm. In the third picture you can actually see how much needs to be cut off in order to match the old shoes.

BTW, the other ends of both old and new shoes match perfectly, that is where the slot that goes towards the "spreader" is located.

Please correct me if I'm wrong on this, but I'm seriously considering sawing the pins of the new shoes down to a size that will match the old shoe's length.

Any suggestions or ideas if I'm on to something here?

Attached Thumbnails

     

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W163 ML230 EURO SPEC 1999
W124 300E 1986