I don't think the cam could be accurately held for grinding the quill in place. Cam grinding is a rough and scary thing to watch. The quill is not available separately. I was scheming to do billet camshafts at the time and needed to see just how BMW had machined the hole in the end of the camshaft. I would consider Loctiting the quill in place. The tricky part would be figuring out where to place it to get the ignition timing right. There have to be tons of used cams out there-I remember seeing drawers full of them when Bob's was still actively selling used parts. I wouldn't hesitate using a 308 in an R60; one of the guys at Bob's is running one in his R60/5, and I have installed R75 and R80 top ends on R60s using the shorter cam.