Cass at Dr Diff has them.
Mopar A-Body 8 3/4" Housing & Axle Package
As the other guys said it is best to change out the springs and hangers. You can look on Craigslist and such for a diff housing but are harder to find now a days and people want just as much as a new one. Also be careful of putting a sway bar in the rear without one in the front as this causes under/over steer and changes how the car handles and could make it easier to spin..
