64-72 F-100 pickups had an optional Dana/Spicer 60 Powerloc diff when the buyer wanted a locking diff. 5 bolt axles (5 on 5 1/2"). Usually came with 3:54 gears (mine does in my 66 F100), but I have had 4:10 sets, and I did see a rate plate /6, 4 speed 4:88. Guessing farm truck. Think 3" tubes. Can't remember the overall width or spring mount (they were on top). Narrower than a square body gm.
