Steve,
Just about a year and half ago I sought the assistance of a few very helpful members of this board to research this car.
Link to that Post.
This car was ordered as a 350 - 3 speed and converted by Dana but not sold as a pre-sale converted car. I still have this car and it has been a blast being involved with the driving, showing, and all the research.
To answer some of your tech question. The fan was an original fiberglass after market fan with a spacer to fit just inside the S/B fan shroud. The S/B bracketry was replaced with what ever was available in parts or from service to complete the conversion. I imagine the 1968 parts were more readily availble OTC than the 1969 parts. Since Dana did conversions pre-sales, the parts department kept parts on hand. I do not know what how many S/B to B/B conversions were since 1967 at Dana.
Rich