My 1958 1 ton dually does not have wheel spacers on the rear, but does on the front. I was not alive in 58 (more or less buying this truck new) but it all looks pretty original to me!
The rear axle (Eaton HO 72) is hub piloted, 8 bolt, 1/2" thread (NOT 9/16). The front axle has a spacer from the hub that puts the front wheels out about 3 inches wider. This makes the front wheel track about in the middle of the rear dual wheels.
This spacer is really connected to the hub tight. It bolts to the hub using the 8 hub lugs. It has it's own 8 lugs that are offset slightly from the hub studs.
I can't recall the exact post a while back when this was discussed, but someone else with a similar year dually had the same setup.
