If you use a 302 I expect even the available 4.10 gears for the Eaton axle will feel like they're holding you back.
Ed mentioned a Dana 70 could work for an axle swap if the right width. I have found the 14 bolt GM axle to be a nicer swap in the AD 1 ton as one version of it is pretty much the perfect width, see sticky thread in this section. 14 bolt also has some quite fast axle ratio choices if needed for some reason. Gears I believe are easier to swap and setup in the 14 bolt (more actual adjustments, fewer shims) than a Dana.
Seems your other questions may have been covered already, but if looking for more input...
In my opinion a 6 cylinder would preserve more of the value and uniqueness of the truck... (why is closer to the original appearance now "unique"?) Would not rebuild a 228 but a 270 or 302 instead.
The 18" wheels and tires are probably fine if in good shape and those wheels are distinctive 1 ton. Otherwise 19.5" wheels exist and are probably a better option if used frequently and or in the long run, best with 8R19.5 tire for the original tall skinny look. There was some discussion and perhaps an example of someone adapting 19.5" rims from a dodge 4500 or similar to the old wheel centers. I think those rims might be a little wide, and would use 6" wide 19.5" rims if possible, and with the original centers with 8 hand holes I think would be the the ideal combo for original looks and modern reliability/function.
No need to switch to single wheels unless you just want to. In which case you need front hubs from a 3/4 or 1 ton single wheel truck. Rear axle is the same except the dually application has longer studs. In my opinion the ideal single wheel is also 19.5" but becoming harder to find than the dual 19.5 wheel.
