The rear end that has the castle nut and cotter pin has a hub and drum assembly mounted on a tapered/keyed axle.
The proper way to get them is to use a three-legged hub puller. Remove the castle nut, cotter pin and washer on axle.Mount the legs to 3 of the lug studs/screws and use a fair-size ball pein to knock the lever until the hub "pops" free. An "old-timer's" method is to use a piece of chain about 12-14 feet long with links large enough to accept the lug studs/screws. Remove the castle nut, cotter pin, and washer.Screw 2 or 3 links to the hub. Lay the rest of the chain out in an "ess"-shape. Grab the end and snap it like a bullwhip. If everything is OK you should be able to "pop" it loose with only one or two snaps.