Don't know if you were able to get an answer on this one or not. For what its worth, the 36-49 Master Chassis Body Parts list shows (Group 8.0286) the clutch housing as P/N 1433146 for 37-40 Cads/LaSalles and P/N 1441676 for 41-48.
hope this helps.
(if you get stuck, I have a set up from a 47 Cad engine that I need to find a home prior to an impending move to a new home)
cad60s@aol.com