Early model A axles had a different drive shaft and pinion which had threads for the adjusting nuts on the drive shaft. Later shafts have the longer pinion with the bearing nut threads as part of the pinion. The model B shaft is a tubular type set up so it's a fair amount larger. This link illustrates a way to push the drive shaft out from inside the banjo center section.
http://www.fordgarage.com/pages/driveshaftremoval.htm