Hi, thanks for spotting this ad. I just checked the and the original part numbers are different for rc41 vs rc40 crown assembly. I doubt there's a physical difference tho, would you have any photos to hand?
DOH! correct as 40's have a circlip on the LH holding in the assembly opposed to the 41's air cap. I do have some 41 crown/stanchions/steerer and damper rod.... so must have some other spares around so will have a dig in the morning for you