Gror,
Nice rebuild project, the pictures are great for reference and for all the other members to enjoy your efforts.
Regarding OT's comments about the bell housing, I was wondering if there was a story behind that as well.
Are you thinking of using birch to replace the rotten wood?
I may be confused about the Model B12 CS - I thought the S stood for "Special", but from the looks of pics #5 & #6 Bombardier must have offered a "Safari" package in 1950.
Looks like you are on the way to having a great unit. Keep the pics posted and Good Luck.