Looking at the years, I'd be almost certain thats a Dana 61. That was the normal axle used in 3/4 ton and 1 ton 80s Ford vans.
Its a bastard dana 60, really. The gearset is different to run high gears, 3.07s, 3.31s, 3.54s.
It is possible, with a special spacer kit, to run Dana 60 gears in it, but might just be better off finding a different rear, if thats the case.
Otherwise, its the same thing as a standard rear dana 60. 9.75" ring gears, full floating 30 spline 1.31" axleshafts (i.e. Dana 44 size shafts)