I just went out to the shop and took a picture of my dually rotors.
Now, I know they look foreign to what you're used to, but the guts, ie the bearings, threaded nut, cotter pin, etc are located down in a recessed well in the center. While the rotor is deep, the spindle itself is way down inside the center bore.
Also, I know for a fact, the center dust cap is the same between 3/4 and 1 tons. I had to order one Friday for my own truck and spent a lot of time looking.
I have heard that the spindles are the same. I know the semi wheel dually crowd often swap rotors around to get different track widths.
If it were me, I'd open two tabs on my browser and catalog the inner bearing, outer bearing, grease seal, upper ball joint, lower ball joint, and outer tie rod ends between 3/4 and 1 tons. I use OReilly Auto Parts website for such projects. It would seem that if all the above parts were the same part number between the 3/4 and 1 ton, the spindle would be the same. No guarantees doing it that way, but it would sure seem very likely.