Thanks for your suggestion, but I may be reading it a bit too late. When the speedo unit arrived, I did consider a swap. What stopped me is that I wasn't sure that would be a correct cure, because my understanding of the differences between DC and SC is limited (for now) to the drive types. I already sent the SC speedo to Marcel. In the end, I hope to get a bit more for the fully functioning DC unit when I decide to sell it.
Regarding the airbox, I'm searching the forum now to find out 1) how to remove the silver paint, and 2) if the serious cracks are repairable. If I cannot find the right thread, I'll start a new one with pics.
Thanks
John