From my experience, I would recommend using the wheel that fit's the front end that you have. I know mine was more difficult using the 950SM brake rotors and calipers than say a 450 EXC using a single brake rotor and KTM wheel. I wanted the keep the tubeless BMW front wheel and did. It took a lot of thought and trial to have a complicated, two piece adapter made for each side. Then another adapter for the BMW axel to the KTM fork legs.
I would go with the BMW head bearings, dust covers. I used all the BMW stuff and turned down and shortened/rethreaded the KTM stem to the right length. That also took a couple of tries to get the right length.