The axle from a Ford van is most likely a Dana 60, not all of them will be the same width, I had one from a Ford van that was too wide. They do have ratio choices but changing gears in a Dana is not quite as easy as in a GM 14 bolt.
The 14 bolt has lots of ratios available even as fast as 3.21 and as slow as 5.38. Also reasonably easy to change gears and set them up, pinion with it's bearings and housing unbolt and slide right out the front.
The 14 bolt from a Cab and Chassis GM truck in my experience are all nominally 62-63" wide, within an inch same as AD 3/4 and 1 ton trucks are.
