It's been awile, so don't quote me, but I believe the homokenetic can be "upgraded" to the annular with some extra parts. I know my 126 can be.

These are #'s from FastLane:

(1) 124 350 56 45 flange (2) 124 357 01 75 washer (1) 124 357 02 89 cap and (6) 000 990 92 12 bolt.

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The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)