Jim, if you go to the discussion group on brakes you'll find quite a few posts on removing rear brake drums. You will need a drum puller like the one pictures - DO NOT use a jaw puller on the edges of the drum or your'll break it for sure. And don't forget to leave the axle nut on loosely so when the drum comes off it won't cause any injury. Here's a link to one of several threads on the topic:viewtopic.php?f=9&t=37
Perhaps we should wait until your mechanic gets the rear axle apart and avoid speculating what parts might be needed. The parts listings have some good illustrations for identifying the parts by number - perhaps you should consider purchasing one? Here's a picture of a senior Packard rear axle probably similar to yours - can you identify what you are looking for?
PS - better yet, enclosing a page from the 1937 Super Eight shop manual, another reprint readily available which you might wish to purchase. Hope this is useful in identifying what you need.