One thing to note on the pre 1947 truck bellhousings is that the clutch and master brake cylinder mount to the bellhousing. A later 47-54 bellhousing is a bolt up change, but it does not have the mounting holes for the pedal assembly. Jim Carter sells bellhousings (1947-1954) that have been modified for the pedal assembly in a pre 1947 truck. A more modern transmission... like the T-5, or muncie, or saginaw will bolt directly to the 47-54, or 55-59, or etc. The later transmissions will not bolt up to a pre 1947 bellhousing.
