That rear end is out of a 73 or newer 30 series van. The shock mounts being reversed from the locations on a 73 or newer pickup is the clue. The van & possibly a "forward control" p- chassis (the kind of boxy truck tool, bread & chip companies use with the flat steep windshield) are the only ones that have shocks positioned like that. If it is from a van, it is probably 4.10's, p- chassis with a 6 cyl. usually 4.56's. The van rear end is preferred by some mud draggers. I believe it is a little wider wheel track than the pickup rear ends. Since a 4x4 front axle has wider wheel track than the rear, It brings the rear tires following the front's ruts better.
If it is the full floating axle type, it has a 10-1/2" ring gear. SUPER TOUGH!
-Jeff
