Usually it does mean everything but sometimes you just can't find the right rear for your application. Especially when you're looking for heavy parts like a rear.....shipping is an issue so you tend to look locally.
You might find a find a complete A body 8.75" but it might be a 2.75 open with the small bolt pattern axles. So now you've got to find a sure grip diff, 3.55" gears and big bolt pattern axles.