The early cars had the rear axle housings with the seams on opposite sides. The cars were delivered with both seams facing forward. They are dimensionally the same and if you reversed them it will put the seams facing aft.
The later cars had the seams on top and if you reversed them they were still on the top.
In 1929 Henry had one supplier that put the seams on the bottom, if you reversed them they were still on the bottom. Seams on the bottom are rare since only a few were produced in 1929.
Apparently when Les Andrews wrote the section of his book about rear axle assembly repair he documented the repair of a rear axle assembly he had in his shop and it had been swapped around with parts from other years.
It is quite common to run into this situation, I have seen it often when overhauling differentials. There are often parts from different years installed. The axle housings are all interchangeable.
If you are restoring a blue ribbon car you should refer to the judging standards, it describes the evolution of the rear axle assembly components over the years of production in detail. And if you are restoring an early car with seams on the sides, face them forward.
Tom Endy