If it's 6 lug, it's problby from a 4x4 GM. As I mentioned, you should be able to find just the axle shafts themselves from a similar year 2wd truck and simply swap the shafts themselves. That will give you the GM 5x5 bolt pattern, also shared with the police and taxi (and later SS Impala) versions of the Caprice. Drums will swap, too.
