Pre 1947 bellhousings mount to the crossmember the same way as the 47-53 bellhousings do, but they use a different transmission bolt pattern, and they have a boss with 3 tapped holes for the brake and clutch pedal which mounts to the bellhousing.

The general rule of thumb when swapping a 235 or 261 for a 216 is to use the bellhousing that came with the truck from the factory, not the bellhousing that came from the newer engine. All the chevy and gmc bellhousings from about 37-59 will interchange on the engines, but not necessarily in the chassis.

John