Graeme,

If you are careful you can reuse most of the fasteners, but be aware that the the bolts have a sealant that waterproofs their penetrations. I swapped my running boards for side skirts and replaced all the fasteners, but I could have reused them. there are two or three per side that require some manipulation to uncover and remove, but if you look at some of the write ups regarding the removal you should be fine. There are some rivets in the wheel wells that will need to be replaced.

Joe

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Gone but not forgotten:
1974 2002
1986 325
1994 325
Now:
2011 X3
2012 X5 Diesel