Front is the same except for a spacer to make the dually rim sit correctly. Rear, is a different matter as the Dana 80 is wider. You might be able to get away with it if the dual in the rear clears the leaf spring. If not, there's spacers. Though I run a spacer in my rear for width, only the outer is supported by the spacer. Supporting both would make me nervous. For the bed, you can get flares from Jcwhitney, but they are pricey.
Boy you must like the look to consider it though. The only reason I got a dually is because I can squeak by with a pallet of concrete in the back. It's a pain to drive. One advantage you would have with a conversion is that if the narrower axle can fit the duals (it will be close) The whole thing will be narrower. 'Course if you can find an 80, then you have the headache of brake fittings, driveline stuff and perch mounts.
Hauling wise, I would note that airbags and e rated tires gets you pretty much there. I am assuming you have the new body style. This info is pretty much for the second generation, as I think the axles are different before that.
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