It’s my recollection that the early style B/RB engines that had the extended crank flange used the auto transmissions with a bolt on bellhousing.
If the trans in the car has what looks like a regular 727 then it does not have that extended crank flange.

The early style extended crank flange has 8 bolt holes and the converter has 8 studs that attach to the crank and held in place with nuts.