Andy,
You will find your choices are really limited if you are keeping the torque tube driveline. A call to Patrick's in Arizona is a must. I believe he has a kit for using the saginaw 4 speed with the torque tube. However, the 1946 has a different bellhousing bolt pattern than the later trucks. The deco and prewar trucks had 3 extra holes drilled in the bellhousing for the brake and clutch pedals. A later 47-54 bellhousing will bolt to the saginaw transmission, and your crossmember with no modifications, but it will not bolt to your brake and clutch pedals. I believe Jim Carter sells an adapted bellhousing for this purpose... to put a later transmission in an earlier truck and bolt the brake and clutch pedals back to the bellhousing like stock.
John
