What I believe happens is that BMW approach Bosch to make a part. Bosch do and sell it to BMW - BMW part number. Bosch may also make it for other engine makers under a that other maker's number and also for themselves under a Bosch part number. The Bosch parts book will only show Bosch part numbers - cheaper to buy than OEM part numbered item as it is handled less. Bosch outlets will not have access to OEM numbers due to confidentiality clauses in the contracts. Does it become clear? The part is the same for all users but numbers change. With all vehicle/engine info you should be able to get a Bosch part from Bosch and fit it with no problems.
Good - Fast - Cheap: Pick any two.
E23 735i; E30 318i; E32 735iL (X 2 - 1 White and 1 Light Blue); E34 535i; E38 735iL; R50 Cooper; R55 Cooper Clubman.
E21 318i; E32 735iL; E34 535i; E38 730iL; E53 4.4i