Its hard to give specific information when you are not sure if you have the original parts or not. But assuming you have the orignal rear axle, the stuff from the 1/2-ton won't swap onto it.
You can swap the entire front axle to get the 6-lug hubs, but in the rear you probably want to swap the axle from a later 6-lug truck.
You probably don't want to swap the 1/2-ton rear axle to the 3/4-ton. Without getting into the details, it would be a lot of work for little gain.
