8 3/4 axle ID help - truck?

In cleaning out the remnants of a deceased friend's garage, I came across a pair of axles that I can't ID. I don't want to scrap them, but can't figure out what they go to. They are clearly for an 8 3/4 rear and still have bearings with one side adjuster in place, BUT THEY ARE 5 1/2 INCH BOLT PATTERN. From the outside face of the stud flange to the end of the axle is 31 1/2 inches. If the Chrysler cars are any indication, it would be from 1965? (they are not spindle nut axles) to 1972 (end of 8 3/4). Anybody have any idea???