4.3, My '48 has the hub you describe as a spacer. It has 6 bolts that hold it to the drum? Do not remove those 6 bolts. Mine requires the removal of the spindle nut under the dust cap. You shouldn't have to lock up the drum, because the spindle is stationary. Just remove the nut,(check for a cotter pin through the spindle) and the hub should slide off. You might have to back off the brakes in order to get the drum to slide over the shoes.
That's how a '48 works, don't know how much help it will be on a '39?
