Your motor does not use Nikasil. BMW stopped using it late 90's. You can have the alumisil block boarded and refinished. Unsure if the 4.8 block can be overboard. The alumisil process is reproducible if the block can be boarded. Check the Porsche sites, they talk about it. There are some other good articles on it also.

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2003 X5 4.6is Estoril Blue
2005 Infiniti G35X
1972 Datsun 240Z
1991 Isuzu Impulse XS Sold
1972 Fiat 850 Spyder Donated
1972 Datsun 240Z Sold
1972 Datsun 510 Sold