They've been discussed before. They were apparently a severe duty piece designed for taxis and maybe police use. A couple of guys chimed in saying that with the iron liner, they end up AT LEAST as heavy as standard 3" HD drums. I think the finned aluminum is used first and foremost for its superior heat dissipation properties.
I am not sure if there are any Galaxie specific aluminum drums. Be careful
when they are advertised, aluminum drums were available on 62-64 Lincoln's. I almost spent allot of money on a pair last year. The clue is the 5x5 bolt pattern. If there are any I would assume the Lincoln drum would have been adapted for the Galaxie 5x4.5 pattern.