Uli,
The oil bowl bulletin (#13) refers to the replacement of the first version finned bowl, which was not ribbed inside and so cracked around the centre boss if the bolt was over-tightened, with the second type finned bowl which had strengthening ribs around the inner boss. The reason the replacement did not apply to engine numbers from 1 to 1782 is presumably because these were factory fitted with the round oil bowl which did not suffer cracking problems.
Just my interpretation of the available info.
Chris R.