Can parts from 2003 X5 4.x fit 2003 X5 3.0?

Not all parts are interchangeable between the two but I would say about 90% of so will work. Go to realoem.com and type in your car and locate the part of interest. Click on the part number and it will show you every car year and model that part is used in as well so you can use that to see if the parts are interchangeable between the models.

Thank you so much!