It is a 9.25 Chrysler rear, shared with a lot of Jeeps, , 2.71 gears most likely, and disc brakes WERE available. Rear disk brakes parts are approaching, but not quite yet, unobtainium.
Die hard New Yorker and Imperial guys ARE looking for the disc brake setup but will not give you big money for it. The bolt pattern was standardized to 5 X 4.5 in '74.