The 97 and 98 have different engines, hence the cats do not interchange, the 98 has a V6 motor with two exhaust banks, the 97 in an inline 6 with all 6 exhaust ports on the passenger side of the car.

You can get a generic cats welded in place of the factory cats.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)