Volvos old enough to have rear drums also have tapered halfshafts, so I deal with getting those drums off regularly. What's needed is a puller that bolts to the lug nut studs, the bigger the better. You can probably get by with a three-legged puller; better yet is a disc that uses all five studs.
I've never worked on a Packard, but it's probably similar (the Volvo brakes are common to Studebaker). There's a castellated nut locked in place with a cotter pin -- pull the pin and take the nut loose, then turn it part way back on reversed, with the pin slots facing in. This is to prevent mushrooming the axle with the puller, and also to keep the drum from flying across the room when it finally pops. Attach the puller, and tighten it all you can -- the one I have has a big handle across the outboard end of the threaded piece that you can hammer on to get some real torque on the thing. The smack the handle as if driving the threaded shaft into the axle. Repeat as needed.
If that doesn't get the drum off, let it sit under tension overnight, then try again. I know of some people who have had success pouring boiling water over the drum, which makes it expand faster than the axle stub, but I haven't had to do that.
Don't use a puller that hooks to the edges of the drum -- you're more likely to break it than pull it on a tapered shaft setup.
