rear end question?

assuming from your post, the "center chunk" drops out the front of the axle housing and the back of the housing does not have a cover plate, It is more than likely a Mopar 8 3/4. Take the wheels and brake drums off, remove the nuts holding the brake backing plates to the end of the axle tubes, ans slide the axle shafts out about 6 ". Then you can remove the bolts holding the chunk in and it comes out the front. (driveshaft has to be disconnected of course)
I agree except for the part about sliding the axle shafts out 6". If you don't plan on changing the seals (I would unless they're new) you don't want to let the axle shaft rub on them or sit with their weight on them or they might get damaged and you'll have the pull it apart again and do some cleanup this time. If you luck into a sure grip or not, you'll also need to set the axle shaft end play. It's VERY important so, if you've never done it before, I'd get a service manual or run a search to check the procedure. It's not difficult.....you basically need a slight amount of end play so the bearings don't overheat but not so loose as to cause leaks and brake problems. Oh, and those 3rd members are kinda heavy and awkward so be carefull handling them. They like to bite fingers too if you get them in the wrong place!