CJ-
I am very familiar with swampers, I've had anywhere from 44s to 33s. I was ready to order 2" spacers from National tire when they told me don't bother the 10. 50s will fit with enough room to slide your pinky as long as DC didn't change the spacing. They are the experts. I asked him 3 or 4 times if he was sure. Either way, the place I will do the work stocks thin spacers, each are a 1/4" wide, so if they are a bit close I will use one or two. I don't haul or tow anything substantial, so that's not a problem.
Yes 10. 5s will work fine on 6" rims, actually it's better because the cross section will measure out thinner. I really don't like the looks of the stock bricks (10 ply), these meats will give the truck some beef with the additional height. No one makes a radial tall thin mud terrain that fits a 17" rim, so these were my only choice.
Flat spots come out after a few miles, especially with this heavy of a truck. And believe it or not, just like some guys like the sound of a loud Cummins, I like some tire whine and swampers are music to my ears!! And this is one dually that will be off roading!!