Drive Shaft 50 3/4 inches Center to Center

FYI, its a -2.25 inch difference from a 7.25 to a 8.75 rear. And a 8.75 equipped Duster has a driveshaft that is .55 short of the "official" dimension that a early A needs, Id look that up. as the Dart and the Valiant had different wheelbases but maybe the same driveshaft dimensions.
Thanks, but I had a Dana60, cheers